All of these modern analyses make implicit or explicit comparisons to sophisticated modern ideas of determinism and libertarianism. Since these ideas are quite complex, we need to identify and separate the original problems from their modern counterparts. And we need to separate the distinct ideas of logical necessity, physical determinism, fatalism, future contingency (denied on the basis of the principle of bivalence), and divine foreknowledge that are often scrambled together in the work of the ancient thinkers.
The very first free will "problem" was whether freedom was compatible with intervention and foreknowledge of the gods.

Before there was anything called philosophy, religious accounts of man's fate explored the degree of human freedom permitted by superhuman gods. Creation myths often end in adventures of the first humans making choices and being held responsible. But a strong fatalism is present in those tales that foretell the future, based on the idea that the gods have foreknowledge of future events. Anxious not to annoy the gods, the myth-makers rarely challenged the implausible view that the gods' foreknowledge is compatible with human freedom. This was an early form of today's compatibilism, the idea that causal determinism and logical necessity are compatible with free will.

The first thinkers to look for explanatory causes (ἀιτία) in natural phenomena (rather than gods controlling events) were the Greek physiologoi or cosmologists. The reasons or rules (λόγοι) behind the physical (φύσις) world became the ideal "laws" governing material phenomena. The first cosmologist was Anaximander (610-546), who coined the term physis (φύσις) and perhaps even the cosmological combination of cosmos (κόσμος), as organized nature, and logos (λόγοσ), as the law behind nature. The Greeks had a separate word for the laws (or conventions) of society, nomos (νόμος).

Heraclitus (535-475) claimed that everything changes ("you can't step twice into the same river") but that there were laws or rules (the logos) behind all the change. The early cosmologists' intuition that their laws could produce an ordered cosmos out of chaos was prescient. Our current model of the universe begins with a state of minimal information and maximum disorder. Early cosmologists imagined that the universal laws were all-powerful and must therefore explain the natural causes behind all things, from the regular motions of the heavens to the mind (νοῦς) of man.

The physiologoi transformed pre-philosophical arguments about gods controlling the human will into arguments about pre-existing causes controlling it. The cosmological problem became a psychological problem. Some saw a causal chain of events leading back to a first cause (later taken by many religious thinkers to be God). Other physiologoi held that although all physical events are caused, mental events might not be. This is mind/body dualism, perhaps the most important of all great dualisms. If the mind (or soul) is a substance different from matter, it could have its own laws different from the laws of nature for material bodies, and agents might originate new causal chains.

The materialist philosophers Democritus and his mentor Leucippus were the first determinists. With extraordinary prescience, they claimed that all things, including humans, were made of atoms in a void, with individual atomic motions strictly controlled by causal laws. Democritus said:

"By convention (nomos) color, by convention sweet, by convention bitter, but in reality atoms and a void."

Leucippus stated the first dogma, an absolute necessity which left no room in the cosmos for chance.

"Nothing occurs at random (maten), but everything for a reason (logos) and by necessity."

οὐδὲν χρῆμα μάτηῳ γίνεται, ἀλλὰ πάντα ἐκ λόγου τε καὶ ὑπ’ ἀνάγκης

The consequence is a world with but one possible future, completely determined by its past. Some even argued for a great cycle of events (an idea borrowed from Middle Eastern sources) repeating themselves over thousands of years.

The first major philosopher to argue convincingly for some indeterminism was probably Aristotle. First he described a causal chain (ἄλυσις) back to a prime mover or first cause, and he elaborated four possible causes (material, efficient, formal, and final). Aristotle's word for these causes was ἀιτία, which translates as causes in the sense of the multiple factors responsible for an event. Aristotle did not subscribe to the simplistic "every event has a (single) cause" idea that was to come later.

Then, in his Physics and Metaphysics, Aristotle also said there were "accidents" caused by "chance (τυχή)." In his Physics, he clearly reckoned chance among the causes. Aristotle might have added chance as a fifth cause - an uncaused or self-caused cause - one he thought happens when two causal chains come together by accident (συμβεβεκός). He noted that the early physicists had found no place for chance among their causes.

Aristotle opposed his accidental chance to necessity:

Nor is there any definite cause for an accident, but only chance (τυχόν), namely an indefinite (ἀόριστον) cause.
(Metaphysics, Book V, 1025a25)2a

It is obvious that there are principles and causes which are generable and destructible apart from the actual processes of generation and destruction; for if this is not true, everything will be of necessity: that is, if there must necessarily be some cause, other than accidental, of that which is generated and destroyed. Will this be, or not? Yes, if this happens; otherwise not.
(Metaphysics, Book VI, 1027a29)

Tracing any particular sequence of events back in time will usually come to an accidental event - a "starting point" or "fresh start" (Aristotle calls it an origin or arche (ἀρχῆ) - whose major contributing cause (or causes) was itself uncaused, e.g., it involved irreducible chance (today's quantum indeterminacy).

Whether a particular thing happens, says Aristotle, may depend on a series of causes that

goes back to some starting-point, which does not go back to something else. This, therefore, will be the starting-point of the fortuitous, and nothing else is the cause of its generation. (Metaphysics Book VI 1027b12-14)

In general, many such causal sequences contribute to any event, including human decisions. Each sequence has a different time of origin, some going back before we were born, some originating during our deliberations.

Beyond causal sequences that are the result of chance or necessity, Aristotle felt that some breaks in the causal chain allow us to feel our actions "depend on us" (ἐφ' ἡμῖν). These are the causal chains that originate within us (ἐv ἡμῖν).

But if it is manifest that a man is the author of his own actions, if we are unable to trace conduct back to any other origins than those within ourselves, then actions of which the origins are within us (ἐν ἡμῖν), themselves depend upon us (ἐφ' ἡμῖν), and are voluntary (ἐκούσια - willed).
(Nichomachean Ethics, III.v.6, 1113b21-22)

Aristotle defends chance (τυχή) as providing a break in any causal chain, but he never says that human free choices are made by chance. Instead, he introduces a tertium quid, a "third thing" that is neither chance (τύχη) nor necessity (ᾶνάγκη). For Aristotle, our decisions are "up to us" (ἐφ ἡμῖν), a phrase that comes closest to our modern free will.

Aristotle knew that many of our decisions are quite predictable based on habit and character, but they are no less free nor we less responsible if our character itself and predictable habits were developed freely in the past and are changeable in the future.

This is the view of some Eastern philosophies and religions. Our Karma has been determined by past actions (even from past lives), and strongly influences our current actions, but we are free to improve our Karma by good actions.

One generation after Aristotle, Epicurus argued that as atoms moved through the void, there were occasions when they would "swerve" from their otherwise determined paths, thus initiating new causal chains. Epicurus argued that these swerves would allow us to be more responsible for our actions, something impossible if every action was deterministically caused. For Epicurus, the occasional interventions of arbitrary gods would be preferable to strict determinism.

Epicurus did not say the swerve was directly involved in decisions. His critics, ancient and modern, have claimed mistakenly that Epicurus did assume "one swerve - one decision" and that "free " actions are uncaused. But following Aristotle, Epicurus thought human agents have the autonomous ability to transcend necessity and chance (both of which destroy responsibility), so that praise and blame are appropriate.

...some things happen of necessity (ἀνάγκη), others by chance (τύχη), others through our own agency (παρ’ ἡμᾶς)....necessity destroys responsibility and chance is inconstant; whereas our own actions are autonomous, and it is to them that praise and blame naturally attach.

Parenthetically, we now know that atoms do not occasionally swerve, they move unpredictably whenever they are in close contact with other atoms. Everything in the material universe is made of atoms in unstoppable perpetual motion. Deterministic paths are only the case for very large objects, where the statistical laws of atomic physics average to become nearly certain dynamical laws for billiard balls and planets.

So Epicurus' intuition of a fundamental randomness in nature was correct. And he agreed with Aristotle that there is another basic kind of causes beyond necessity (άνάyκη) and chance (τυχῆ). They both said our actions are "up to us" (ἐφ' ἡμῖν or παρ’ ῆμᾶς). How exactly determinism and chance relate to autonomous agent causality is not made clear by either of them, and it remains a challenge for theories of free will.

We know Epicurus' work largely from the Roman Lucretius and his friend Cicero.

Lucretius, a strong supporter of Epicurus, saw the randomness as enabling free will, even if he could not explain exactly how, beyond the fact that random swerves would break the causal chain of determinism.

Again, if all motion is always one long chain, and new motion arises out of the old in order invariable, and if the first-beginnings do not make by swerving a beginning of motion such as to break the decrees of fate, that cause may not follow cause from infinity, whence comes this freedom (libera) in living creatures all over the earth, whence I say is this will (voluntas) wrested from the fates by which we proceed whither pleasure leads each, swerving also our motions not at fixed times and fixed places, but just where our mind has taken us? For undoubtedly it is his own will in each that begins these things, and from the will movements go rippling through the limbs.

Lucretius' "first beginning" (primordia motus principium) seems to be a reference to Aristotle's starting point (ἀρχῆ)) and a kind of causa sui that would start additional new causal chains under the control of the mind ("just where our mind has taken us").

The Latin original libera in "whence comes this freedom" has often been translated as "free will," influenced perhaps by the centuries-old free will debate.

But Lucretius himself clearly distinguishes the "free" (libera) from the "will" (voluntas).

If there is free will, all things do not happen according to fate; if all things do not happen according to fate, there is not a certain order of causes; and if there is not a certain order of causes, neither is there a certain order of things foreknown by God.

Epicurus saw that if the atoms travelled downwards by their own weight; we should have no freedom of the will [nihil fore in nostra potestate], since the motion of the atoms would be determined by necessity. He therefore invented a device to escape from determinism: he said that the atom while travelling vertically downward by the force of gravity makes a very slight swerve to one side. This defence discredits him more than if he had had to abandon his original position.

It was the Stoic school of philosophy that solidified the idea of natural laws controlling all things, including the mind. Zeno of Citium, the original founder of Stoicism, had a very simplistic but powerful idea of the causal chain compared to Aristotle.

The Stoic influence persists to this day, in philosophy and religion. Most of the extensive Stoic writings are lost, probably because their doctrine of fate, which identified God with Nature, was considered anathema to the Christian church. The church agreed that the laws of God were the laws of Nature, but that God and Nature were two different entities. In either case strict determinism follows by universal Reason (logos) from an omnipotent God. Stoic virtue called for men to resist futile passions like anger and envy. The fine Stoic morality that all men (including slaves and women) were equal children of God coincided with (or was adopted by) the church. Stoic logic and physics freed those fields from ancient superstitions, but strengthened the dogmas of determinism that dominate modern science and philosophy, especially when they explicitly denied Aristotle's chance as a possible cause.

The major developer of Stoicism, Chrysippus, took the edge off strict necessity. Like Democritus, Aristotle, and Epicurus before him, he wanted to strengthen the argument for moral responsibility, in particular defending it from Aristotle's and Epicurus' indeterminate chance causes.

Whereas the past is unchangeable, Chrysippus argued that some future events that are possible do not occur by necessity from past external factors alone, but might (as Aristotle and Epicurus maintained) depend on us. We have a choice to assent or not to assent to an action. This is a controversial idea and may be inconsistent with orthodox Stoic doctrines, since it suggests the existence of alternative possibilities and the capacity to do otherwise.

Chrysippus said our actions are determined (in part by ourselves as causes) and fated (because of God's foreknowledge), but he also said correctly that they are not necessitated, i.e., pre-determined from the distant past. Chrysippus would be seen today as a compatibilist, as was the Stoic Epictetus. He also has a strong element of agent-causalism.

Alexander of Aphrodisias (c.150-210), the most famous commentator on Aristotle, wrote 500 years after Aristotle's death, at a time when Aristotle and Plato were rather forgotten minor philosophers in the age of Stoics, Epicureans, and Skeptics. Alexander defended a view of moral responsibility we would call libertarianism today. Greek philosophy had no precise term for "free will" as did Latin (liberum arbitrium or libera voluntas). The discussion was in terms of responsibility, what "depends on us" (in Greek ἐφ ἡμῖν).

Alexander believed that Aristotle was not a strict determinist like the Stoics, and Alexander himself argued that some events do not have pre-determined causes. In particular, man is responsible for self-caused decisions, and can choose to do or not to do something, as Chrysippus argued. However, Alexander denied the foreknowledge of events that was part of the Stoic identification of God and Nature.

Most of the ancient thinkers recognized the obvious difficulty with chance (or an uncaused cause) as the source of human freedom. Even Aristotle described chance as a "cause obscure to human reason" (ἀιτιάν ἄδελον ἀνθρωπίνᾠ λογισμῶ).

Actions caused by chance are simply random and we cannot feel responsible for them. But we do feel responsible. Despite more than twenty-three centuries of philosophizing, most modern thinkers have not moved significantly beyond this core problem of randomness and free will for libertarians - the confused idea that free actions are caused directly by a random event.

In his 1896 Studi lucreziani (p.126),Giussani put forward the idea that Epicurus' atomic swerves are involved directly in every case of human free action, not just somewhere in the past that breaks the causal chain of determinism. This goes beyond Epicurus and leads to the mistaken conclusion that the swerves directly cause actions.

The complete conception of the will according to Epicurus comprises two elements, a complex atomic movement which has the characteristic of spontaneity, that is, is withdrawn from the necessity of mechanical causation: and then the sensus, or self-consciousness in virtue of which the will, illuminated by previous movements of sensation, thought, and emotion, profits by the peculiar liberty or spontaneity of the atomic motions, to direct or not to direct these in a direction seen or selected. (Cyril Bailey translation)

Cyril Bailey

In 1928 Bailey agreed with Giussani that the atoms of the mind-soul provide a break in the continuity of atomic motions, otherwise actions would be necessitated. Bailey imagined complexes of mind-atoms that work together to form a consciousness that is not determined, but also not susceptible to the pure randomness of individual atomic swerves, something that could constitute Epicurus' idea of actions being "up to us" (πὰρ' ἡμάς).

It is a commonplace to state that Epicurus, like his follower Lucretius, intended primarily to combat the 'myths' of the orthodox religion, to show by his demonstration of the unfailing laws of nature the falseness of the old notions of the arbitrary action of the gods and so to relieve humanity from the terrors of superstition. But it is sometimes forgotten that Epicurus viewed with almost greater horror the conception of irresistible 'destiny' or 'necessity', which is the logical outcome of the notion of natural law pressed to its conclusion. This conclusion had been accepted in its fulness by Democritus, but Epicurus conspicuously broke away from him: 'it were better to follow the myths about the gods than to become a slave to the "destiny" of the natural philosophers: for the former suggests a hope of placating the gods by worship, whereas the latter involves a necessity which knows no placation'. Diogenes of Oenoanda brings out the close connexion with moral teaching: 'if destiny be believed in, then all advice and rebuke is annihilated'. If any ethical system is to be effective it must postulate the freedom of the will. If in the sphere of human action too 'destiny' is master, if every action is the direct and inevitable outcome of all preceding conditions and man's belief in his own freedom of choice is a mere delusion, then a moral system is useless: it is futile to tell a man what he ought or ought not to do, if he is not at liberty to do it. Here at all events 'destiny' must be eliminated. It is a more fatal enemy than superstition, for it means complete paralysis: spontaneity — voluntas — must be at all costs maintained.

But why, in order to secure this very remote object, should a protest against 'inexorable necessity' be made at this point in the physical system? It would have been easy, one might think, to accomplish the immediate purpose of securing the meeting of the atoms in their fall through space by some device, such as the Stoic notion that all things tend to the centre,' which should not be a breach of the fundamental law of causality, instead of this sporadic spontaneous deviation. And in what sense can this 'swerve' be said to be vital for the freedom of the will, with which Lucretius so emphatically connects it? The answer must be looked for in the very material notions of Epicurus' psychology, which may be briefly anticipated here. The mind (νοῦς) is a concentration in the breast of an aggregate of very fine atoms, the same in character as those which, distributed all over the body and intermingling with the body atoms, form the vital principle (ψυχή). This aggregation of atoms may be set in motion by images, whether coming directly from external things or stored up as an 'anticipation' (πρόληχις) in the mind itself. Suppose, for instance, that in this way there comes before my mind the image of myself walking: ultimately the atoms of the mind being themselves stirred, will set in motion the atoms of the vital principle: they in turn will stir the atoms of body, the limbs will be moved and I shall walk. But before this can happen another process must take place, the process of volitional choice.

When the image is presented to the mind it does not of itself immediately and inevitably start the chain of motions which results in the physical movement; I can at will either accept or reject the idea which it suggests, I can decide either to walk or not to walk. This is a matter of universal experience and it must I not be denied or rejected.

Bailey identifies one swerve with volition

But how is this process of choice to be explained on purely material lines? It is due, said Epicurus, to the spontaneous swerving of the atoms: the act of volition is neither more nor less than the 'swerve' of the fine atoms which compose the mind. The fortuitous indeterminate movement of the individual atoms in the void 'is in the conscious complex (concilium) of the mind transformed into an act of deliberate will. The vital connexion, indeed the identity of the two processes is clearly brought out by Lucretius at the close of his exposition of the theory: 'but that the very mind feels not some necessity within in doing all things, and is not constrained like a conquered thing to bear and suffer, this is brought about by the tiny swerve of the first-beginnings in no determined direction of place and at no determined time'. It is not merely, as has been suggested, that Epicurus decided to get over two difficult problems in his system economically by adopting a single solution, but that he perceived an essential connexion between them: if freedom is to be preserved, it must be asserted at the very basis of the physical world.

The 'swerve' of the atoms is, no doubt, as the critics have always pointed out, a breach of the fundamental laws of cause and effect, for it is the assertion of a force for which no cause can be given and no explanation offered. For if it be said that the atom swerves because it is its nature to do so, that is merely to put 'nature' as a deus ex machina on a level with 'necessity' as it was conceived by some of the early physicists, a force which came in to do what could not otherwise be explained. But it was no slip or oversight on Epicurus' part which a more careful consideration of his principles might have rectified. On the contrary it was a very deliberate breach in the creed of 'necessity' and is in a sense the hinge on which the whole of his system turns. He wished to secure 'freedom' as an occasional breach of 'natural law'. If criticism is to be brought against him, it must not be on the technical ground of inconsistency in this detail, but on the broader ground that in his system as a whole he was attempting the impossible. To escape from the old notion of the divine guidance of the world, the Atomists had set up a materialist philosophy directed solely by uniform laws of cause and effect. Democritus saw that this, if pursued to its logical conclusion, must lead to an unflinching determinism, which with more scientific insight perhaps, but less care for his ethical precepts, he had wholly accepted. Epicurus, unwilling in this way to risk his moral system, tried to escape from the impasse without abandoning a materialist position.

Bailey says some metaphysical agency is necessary to explain freedom

Such a compromise is in reality impossible: a wholly materialist view of the world, which excludes altogether the spiritual and the supernatural, must lead to determinism, and there is no real path of escape, except in the acknowledgement of other than material conditions and causes. From the point of view of ultimate consistency, the 'swerve' is a flaw in Epicureanism, but it is not to be treated as a petty expedient to get over a temporary difficulty, or an unintelligent mistake which betrays the superficial thinker.

It may not be uninteresting to notice that a parallel difficulty arises for modern thinkers and that a solution not unlike that of Epicurus' atomic swerve has sometimes been propounded.
(Bailey, The Greek Atomists and Epicurus, pp. 318-321)

In a single atom the swerve is merely random chance

Of what nature then is this self-initiated movement? In the individual atom it is automatic, spontaneous, and wholly undetermined in occasion or direction. Is the movement of the mind in will merely the result of such a movement in one of its component atoms, or even the sum of many such movements? If so it too must be automatic and undetermined. When the image of action is presented to the mind, it is impossible to foretell in what way the movement will occur, or even whether it will occur at all. In other words the mind is not really self-determined, but is at the mercy of wholly undetermined movements inside itself, and freewill after all its careful preservation turns out to be nothing better than chance. This is indeed the conclusion reached by one modern critic, and it is not to be wondered at that he is unwilling to believe that Epicurus himself can have rested the claim for freewill on the atomic 'swerve'. But the solution of this difficulty lies once again to the Epicurean conception of a compound body (concilium, conciliatus).

In a large number of atoms compounded as a "mind," the swerve of many atoms becomes the free volition of an undetermined consciousness.

The compound is more than a mere aggregate of independent atoms: it is their union in a complex, which has a new individuality of its own in which it may acquire qualities and even powers which are not possessed by the individual component atoms. The soul or mind is a compound body of such peculiar constitution in the nature of its component atoms and their motions among themselves, that it acquires the power of sensation or consciousness.
The automatic swerve of the individual atoms then is translated in the complex of the mind into a consciously spontaneous movement, in other words into a movement of volition.

'The complete conception of the will according to Epicurus, Giussani argues in an admirable summary of his position, 'comprises two elements, a complex atomic movement which has the characteristic of spontaneity, that is, is withdrawn from the necessity of mechanical causation: and then the sensus, or self-consciousness in virtue of which the will, illuminated by previous movements of sensation, thought, and emotion, profits by the peculiar liberty or spontaneity of the atomic motions, to direct or not to direct these in a direction seen or selected.' In other words the blind primitive 'swerve' of the atom has become the conscious psychic act. It may be that this account presses the Epicurean doctrine slightly beyond the point to which the master had thought it out for himself, but it is a direct deduction from undoubted Epicurean conceptions and is a satisfactory explanation of what Epicurus meant:

that he should have thought that the freedom of the will was chance, and fought hard to maintain it as chance and no more, is inconceivable.

And if the further question is asked how can a complex of blind spontaneous movements of atoms become the conscious act of volition of the mind, we are only thrown back once more on the ultimate difficulty, which has made itself felt all through this account of the soul. For indeed, if we look back over it, we find that here and there crudities of thought or incoherences in the connexion of ideas have been noted, yet as a whole the general theory is self-consistent and complete; but at the back of it always lies the difficulty which must beset Epicureanism or any other form of materialism: can the movement of insensible particles produce or account for consciousness? That all forms of consciousness have their physical counterpart, that sensation, thought, will are accompanied by material movements of parts of the physical organism is credible, and indeed scientific investigation seems to be revealing this parallelism more and more clearly to us. The more material thinkers of our own time are content to say that consciousness 'supervenes' as an 'epiphenomenon' on the movements of matter: Epicurus went the step farther and was prepared to say that consciousness, sensation, thought, and will are the movements of the soul-atoms. Such an idea is to most modern minds, as it was to the majority of philosophers in Epicurus' day, unthinkable: between the one set of facts and the other there is a great gulf fixed: nothing can bridge the gulf that lies between the most elementary sensation and the atomic vibrations which accompany and condition it. If we accept a purely materialistic system in any form, its conclusions will have to be mutatis mutandis something like those of Epicurus: but he has done nothing to bridge over the abyss or to make the gulf seem less wide. Consequitur sensus, inde voluntas fit, his pupil says glibly, but each time rouses in us the same feeling that this is just what can never be understood.

And if it is impossible to accept his account of the nature of the soul and its workings, so the inference from it cannot be admitted. If the soul is a mere atomic complex, a 'body', then no doubt like the body it perishes and cannot have any sort of existence after death. But if that account be unsatisfactory, then the problem of survival remains open: the soul may or may not survive bodily death, but the question cannot be decided on the basis of a purely material analysis.

It is impossible in dealing with a material system to refrain from pointing out its fundamental weakness, but in an attempt to estimate Epicurus as a thinker, it is less profitable to quarrel with his base-principles than to think of the superstructure he has built upon them. And once again in examining the account of the soul, for all its weaknesses, we are conscious of the workings of a great mind, capable of grasping alike broad ideas and minute details of elaboration. We are certainly not left with the picture of a moral teacher, who merely patched together any kind of physics and metaphysics to back up his ethical preaching.
(Bailey, The Greek Atomists and Epicurus, pp. 435-37)

David Furley

In 1967 Furley examined the ideas of Giussani and Bailey and de-emphasized the importance of the swerve in both Epicurus and Lucretius so as to defend Epicurus from the "extreme" libertarian view that our actions are caused directly by random swerves. (Bailey had also denied this "traditional interpretation.") Furley argues for a strong connection between the ideas of Aristotle and Epicurus on autonomous actions that are "up to us."

If we now put together the introduction to Lucretius' passage on voluntas and Aristotle's theory of the voluntary, we can see how the swerve of atoms was supposed to do its work. Aristotle's criterion of the voluntary was a negative one: the source of the voluntary action is in the agent himself, in the sense that it cannot be traced back beyond or outside the agent himself. Lucretius says that voluntas must be saved from a succession of causes which can be traced back to infinity. All he needs to satisfy the Aristotelian criterion is a break in the succession of causes, so that the source of an action cannot be traced back to something occurring before the birth of the agent. A single swerve of a single atom in the individual's psyche would be enough for this purpose, if all actions are to be referred to the whole of the psyche.

But there is no evidence about the number of swerves. One would be enough, and there must not be so many that the psyche exhibits no order at all; between these limits any number would satisfy the requirements of the theory.

The swerve, then, plays a purely negative part in Epicurean psychology. It saves voluntas from necessity, as Lucretius says it does, but it does not feature in every act of voluntas. There is no need to scrutinize the psychology of a voluntary action to find an uncaused or spontaneous element in it. The peculiar vulnerability of Epicurean freedom — that it seemed to fit random actions, rather than deliberate and purposive ones — is a myth, if this explanation is correct.

We can now understand why the swerve gets no mention in Lucretius' account of voluntary action. It gets no mention because it plays no direct part in it. The theory of the swerve asserts merely that our actions are not caused conjointly by the environment and our parentage. There was no need for Lucretius to mention this in his account of the psychology of action, any more than there was for Aristotle to insist on his negative criterion of the voluntary in De Motu Animalium.

It may be objected that a swerve in the psyche must have been supposed to produce some observable effect. But not even this is true. We have already glanced at Lucretius' doctrine that the mind has before it innumerable simulacra which never reach the level of consciousness, because the time interval during which they are present is imperceptibly small. But if the impact of those complicated atomic configurations which constitute simulacra could have no observable effect, it is a safe inference that the minute swerve of a single atom would be undetectable. So we can, after all, make use of the Epicurean concept of the concilium in our explanation. I argued previously against Bailey's use of it in saying that "what in the individual atom is a matter of chance, in the conscious complex of the animus is 'conscious chance.'" It is impossible to see how the random motion of an individual atom can by itself account for the end-directed motions of the complex of which it is a part. It is perfectly reasonable, however, that the random motion of a single atom should be concealed by the fact that it is just one element in a complex.

The Epicurean psychology of action, if I am right, was in outline as follows.

Each person is born with a psyche of a particular character, determined by the proportions of atoms of the four different kinds which constitute a psyche. From the beginning of life, reactions occur between the psyche and the external world, through the medium of atomic eidola which flow from all objects and may reach the psyche through the sense organs and the mind. From the beginning, the child experiences feelings of pleasure and pain; in atomic terms, pain is a disturbance of the motions of the psyche atoms caused by a lack of something, and pleasure is either the restoration of the undisturbed motions which constitute tranquillity, or else the state of tranquillity itself. The child learns to associate external objects with one or other of these feelings. A feeling of something lacking constitutes a motive to make good the lack, and so creates an impulse towards an object in the external world which the child has learned will supply the deficiency.

A person's feelings, and therefore his motives and his behavior, are to some extent determined by his genetic inheritance of a psyche of such and such a constitution.

Swerves allow psychological character development (cf. Robert Kane's "self-forming actions")

But the motions of the psyche (and it is in its motions that all its character and action consists) are not determined ab initio, because a discontinuity is brought about by the atomic swerve. The swerve of an atom or atoms in the psyche means that the inherited motions are disturbed, and this allows new patterns of motion to be established which cannot be explained by the initial constitution of the psyche.

There is both continuity and discontinuity. The character of the person is to some extent still determined by the initial constitution of his psyche, because the proportions of atoms of different types in it remain the same. But to a much greater extent his character is adaptable, because the motions of the atoms are not determined and can be changed by learning.

A person learns by experience. He learns what desires must be satisfied, and what objects satisfy them, simply by constant repetition of the experience of desire and satisfaction. He can learn by individual trial and error, or by precept and example from others. If he is indoctrinated in the Epicurean philosophy, he learns to distinguish desires which arise from nature and must be satisfied from those which arise from nature but need not be satisfied and from those which do not arise from nature and are best eliminated. He learns that the limit of pleasure is the absence of pain, and so ceases to feel pain through desire for some extra pleasure. His feelings become disciplined, so that an improper object—one that brings more pain than pleasure in the long run—no longer arouses desire in him. He learns not so much to reject some of the things he desires as to cease to desire the things he ought to reject.

The wise Epicurean is not to be pictured as asserting himself by repeated "acts of volition" against the temptations of the world, but as having learned not to be tempted. His "freedom" does not consist in being presented with possible alternatives, and in choosing one when he might have chosen the other. It consists rather in the fact that his psyche is the product of his own actions and is not unalterably shaped by some "destiny" from the time before his birth.

The weakness of this theory of "freedom," both in its Epicurean and in its Aristotelian form, is to be found chiefly in its refusal to consider the processes of character formation. When Aristotle says that children should be brought up from the beginning to feel pleasure and pain in the right objects, he obviously does not consider such education to be equivalent to compulsion. He stresses that educators and lawgivers use punishments and other incentives to make people behave in the right way, and at the same time insists that the acts which create virtuous dispositions are not to be referred to causes outside ourselves." It is curious that he does not see this as a problem, since it was clearly raised by Gorgias in his Praise of Helen, almost a century before, when he offered as one of his excuses for Helen's behavior the possibility that she was persuaded by argument. It might well have arisen, too, from a consideration of Democritus' ethical opinions. Part of the explanation is probably that persuasion was commonly seen as an antithesis to compulsion? But Aristotle should have seen the need to reestablish this antithesis, since he had to some extent broken it down himself in talking of a class of actions which were a mixture of the voluntary and the involuntary.

If Aristotle had seriously examined the reasons why he took the results of education to be "in our own power," he would have been compelled to specify more exactly what he meant by saying "the source is in us." He might then have been led to say that the criterion of morality (that is to say, the criterion that determines whether an action is liable to moral appraisal or not) is to be found precisely in our ability to be influenced by persuasion as opposed to force. If he had stressed this, then I think Epicurus might after all have thought the swerve unnecessary (unnecessary, that is to say, in his psychology; it was still needed in his cosmology). For in his theory, the effects of persuasion would be similarly explained whether the swerve were there or not. Persuasion is by words, and words, in the crude atomism of the time, do their work by collisions, through the medium of the sense organs. The swerve is not needed for them to have this effect.

I leave it to others to decide whether the Epicurean theory, without the swerve, would have been "determinist" as opposed to "libertarian," because I do not yet see how to define this particular antithesis. But if it would be determinist, I think it would be a sort of determinism that is compatible with morality.
(Furley, Two Studies in the Greek Atomists, pp.232-236)

In the same year 1967, Huby suggested that Epicurus was the original discoverer of the "freewill problem." Huby noted that there had been two main free will problems, corresponding to different determinisms, namely theological determinism (predestination and foreknowledge) and the physical causal determinism of Democritus.

It is unfortunate that our knowledge of the early history of the Stoics is so fragmentary, and that we have no agreed account of the relations between them and Epicurus. On the evidence we have, however, it seems to me more probable that Epicurus was the originator of the freewill controversy, and that it was only taken up with enthusiasm among the Stoics by Chrysippus, the third head of the school.

The outlines of Epicurus' approach are familiar enough. He took over the atomic theory of Democritus almost unchanged, but introduced one significant new point, the swerve of the atoms, a slight change of direction that could occur without any cause. According to tradition this was to solve two problems for him: the change of direction would enable atoms otherwise falling all in the same direction and at the same speed to collide and so enter into larger combinations, and the fact that it occurred without cause would break the otherwise continuous chain of causation and so allow room for freedom of action by men, whose minds were composed of atoms and therefore subject to the same laws as everything else.

In spite of the poverty of our evidence, it is quite clear that one main reason Epicurus had for introducing the swerve, or rather the swerve as a random, uncaused event, was as a solution to the problem of freewill. Unlike Aristotle, he fully appreciated that there was a problem. He believed in free will, because it seemed to him manifestly clear that men could originate action, but he could not, like Aristotle, regard this as the end of the matter. We may not think much of the solution he offers, but he deserves full credit for appreciating the problem.

There are now two main points to be cleared up: (1) was Epicurus the first to appreciate the problem, or was he anticipated by the Stoics or someone else? (2) If he was the first, how did he come to do so, and what exactly was the nature of the problem as he saw it?

...we have to explain why Aristotle was so resistant to determinism, and Epicurus so impressed by it. The answer must surely lie, in part at least, in their differing attitudes to Democritus. Aristotle was indeed steeped in Democritus, and had a considerable admiration for him, but at the same time found his system quite unacceptable. We can see why this was so. Aristotle's thought was dominated by a teleological view of causality, in which the paradigm of what guides change is the tendency of an organism to develop into a certain kind of thing. This made the idea of a causal chain in which the future is entirely determined by the past strange and irrelevant.

...in Book K (1064b 35) Aristotle takes his stand on the point that we know very well that some things happen kata symbebekos, which is in opposition to ex anankes, and that, in this context, means causally determined in our sense. What happens kata symbebekos is, then, undetermined. Aristotle then had two reasons for rejecting determinism, (i) that some things obviously happened kata symbebekos, and (ii) that men had free will [Aristotle only says some actions are "up to us."] At the same time it is putting it too strongly to say that he rejected determinism: rather it seems that it was for him a non-starter. This is clearly in sharp contrast to the views of Epicurus and the Stoics, both of whom made valiant if unsuccessful attempts to reconcile freedom and determinism.

...the fact remains, on the evidence of Cicero and Lucretius, that Epicurus still ultimately traced the freedom of the will to the swerve of the atoms. How exactly he did this remains a mystery.

The philosophical, as distinct from the historical, conclusion of my argument is twofold, first that it was possible for men like Plato and Aristotle to hold many educational and psychological beliefs in common with us without being aware of any freewill problem because they had no notion of thorough-going psychological determinism, and, second, that once the problem had been formulated it was appreciated by philosophers of many different schools throughout later antiquity as if it were indeed a natural problem.
(Pamela Huby, "The First Discovery of the Freewill Problem", Philosophy, 42 (1867), pp.353-62)

Richard Sorabji

Sorabji's 1980 Necessity, Cause, and Blame surveyed Aristotle's positions on causation and necessity, comparing them to his predecessors and successors, especially the Stoics and Epicurus. Sorabji argues that Aristotle was an indeterminist, that real chance and uncaused events exist, but never that human actions are uncaused in the extreme libertarian sense that some commentators mistakenly attribute to Epicurus.

Aristotle accepted the past as fixed, in the sense that past events were irrevocable. But future events cannot be necessitated by claims about the present truth value of statements about the future. Aristotle does not deny the excluded middle (either p or not p), only that the truth value of p does not exist yet. Indeed, although the past is fixed, the truth value of past statements about the future can be changed by the outcome of future events.

This book centres on Aristotle's treatment of determinism and culpability. One of the advantages of studying Aristotle's treatment of determinism is that we get a sense of what a multiform thesis it is. Arguments from causation are by no means the only ones that have been used to support it, and Aristotle is the grandfather, even if not the father, of many of these arguments. I am not myself convinced by any of the arguments for determinism, nor by the arguments that it would be compatible with moral responsibility. But in order to discuss the question, I shall have to consider some very diverse topics: cause, explanation, time, necessity, essence and purpose in nature.

These are all subjects of intense controversy today, and time and again Aristotle's discussions are intimately bound up with modern ones. Often, I believe and shall argue, we can benefit from going back to the views of another period, views which are sometimes refreshingly different from our own. I shall try to explain, when necessary, where those differences lie. The discussion will not be confined to Aristotle. I shall try to supply a historical perspective and a sense of continuity, by seeing how the views of his successors and predecessors fit on to his own. But at the same time it will remain a central aim to build up a picture of Aristotle's own position on determinism and culpability, by tracing it through the many areas of his thought.

By determinism I shall mean the view that whatever happens has all along been necessary, that is, fixed or inevitable. I say 'whatever happens', meaning to cover not merely every event, but every aspect of every event — every state of affairs, one might say. I shall make no further attempt to define necessity, although various kinds of necessity will come to be distinguished as we go along. I have deliberately defined determinism by reference, not to causation, but to necessity. I have not defined determinism as a view which denies us moral responsibility. The latter idea, often known as `hard' determinism is comparatively rare, and was rarer still in antiquity. Many determinists have tried to argue that it is not a consequence of their position. I believe that it is a consequence, but not usually an intended one. I have spoken of things as having 'all along' been necessary, because there would be little moral interest in a view which declared that things became necessary at the last moment, or irrevocable once they had happened. Indeed, Aristotle admits the point about irrevocability; what he denies is that everything has been necessary all along.

I shall be representing Aristotle as an indeterminist; but opinions on
this issue have been diverse since the earliest times...

It is not always recognised that Aristotle gave any consideration to causal determinism, that is, to determinism based on causal considerations. But I shall argue that in a little-understood passage he maintains that coincidences lack causes. To understand why he thinks so; we must recall his view that a cause is one of four kinds of explanation. On both counts, I think he is right. His account of cause, I believe, is more promising than any of those current today, and also justifies the denial that coincidences have causes.

There is another strut in the causal determinist's case. Besides the view that everything has a cause, he holds that whatever is caused or explicable is necessitated. If this idea is once accepted, he has a powerful argument, already wielded by the Stoics, against the indeterminist: any action that is not necessitated becomes causeless, inexplicable and hence a thing for which no one can be held responsible. On this issue, regrettably, Aristotle is less firm; he wavers on whether what is caused is necessitated. But insofar as he sometimes implies that it is not, we will be better placed, later in the book, to understand the argument of Nicomachean Ethics III 5. In denying that voluntary actions have been necessary all along, Aristotle need not be implying that something is uncaused.

The best-known arguments in Aristotle on determinism have to do with time rather than cause. In Int. 9, he tries to reply to the deterministic 'sea battle' argument which is based on considerations of time and truth...I shall distinguish certain further deterministic arguments based on the necessity of the past, or on divine foreknowledge. The only one of these arguments articulated by Aristotle (and opposed by him) is the sea battle argument. But he is a more or less remote ancestor of many of the others, and of some of the answers to them.

I shall have shown by the end of Chapter Eight why I think Aristotle an indeterminist. I do not believe that he came close to the determinism of Diodorus Cronus, or of the author of the sea battle, nor that he treated coincidences as necessary. In a later chapter (Fourteen), I shall further deny that he treated all human action as necessary. But it will be time in Chapter Nine to guard against the ascription to him of too extreme an indeterminism. His occasional denials that natural events can ever occur of necessity seem to be contradicted elsewhere. Certainly, his belief that there is purpose in nature does not require, and is not thought by to require, the denial of causal necessitation. To show why such a denial is not required, I shall have to try to show how Aristotle's purposive explanations in biology work. It will be argued that they work in several different ways, and that most of these ways leave Aristotle immune to modern criticisms of purposive explanation in biology. Criticism of Aristotle here has been widepread and vitriolic; I hope to show that it is largely mistaken.
(Necessity, Cause, and Blame, pp. ix-xii)

Sorabji claims that he can separate necessity from causality, with implications for causal determinism. In particular, he defends indeterminists against the charge that libertarian decisions are unintelligible.

[If] some of our decisions are not necessitated, it by no means follows that they are uncaused or inexplicable. If this is correct, it should answer the causal determinist's argument that, if some of our decisions are not necessary in advance, they will be inexplicable and mysterious happenings of which we cannot be held responsible. The answer suggested here is that from our decisions being unnecessitated it would not follow that they were inexplicable, or uncaused.

The above reflections have implications not only for the common charge against the indeterminist - that he renders decisions inexplicable, but also for some of the premises that are typically used for establishing the determinist's case. For we have been led to doubt the premises that every state of affairs has a cause and that whatever is caused is necessitated.

Even these two premises together would not be enough to yield the determinist's view that whatever happens is necessary in advance. To obtain that result, he may appeal to the idea of a sequence of causes: each state of affairs has a prior state of affairs as its cause. If this seems implausible, because the dent in a springy cushion is caused by the contemporary presence of a weight, it will suffice if in any causal chain a proportion of the causes are prior. On the other hand, if the determinist allows that a cause is only a part of some necessitating conditions, he will have to be willing to argue that the complete set of necessitating conditions commonly exists in advance of its effect.
(p. 32)

Sorabji considers the suggestions that quantum uncertainty disproves determinism, and he finds that Aristotle described "starting points" (ἄρχαι) for new causal chains that resemble probabilistic quantum events.

The appeal to the totality of laws and of initial conditions brings us closer to the classic formulation of causal determinism by Laplace.

[But], the current state of physics no longer offers the encouragement that was once expected. By an ambitious extrapolation from the successes of Newtonian mechanics in the field of astronomy, Laplace was able to think of science as on the determinist's side. But the majority" of quantum physicists now maintain that their science actually contradicts determinism. or certain micro-events are not made necessary in advance of their occurrence. Sometimes an attempt is made to admit this conclusion, but reduce its interest, by maintaining that indeterminacy at the level of micro-events will not lead to indeterminacy at the level of the large-scale events that concern us in real life. But against this we have already noticed examples of a small-scale indeterminacy being amplified into a large-scale indeterminacy through radio-active material being connected to a bomb or a living organ.
(pp. 35-6)

None of this is intended to rule out the causal determinst's view as possible. I do not know how to do that. But it is meant to place an onus on him to argue for his case, if he wants it to seem at all plausible. I cannot say that I think of it at the moment as having any plausibility.
And I should certainly hope that it was false. For I believe it is determinism that rules out moral responsibility and other things we believe in. I believe it is a necessary, though a sufficient, condition of our being morally responsible agents that actions should not all along have been necessary. I do not think the indeterminacies of quantum physics help in any direct way to preserve moral responsibility. What is important is that, in the different sphere of
human conduct, there should be actions which are explicable without being necessitated.
(pp. 37)

Finally, although he thinks Aristotle was not aware of the "problem" of free will vis-a-vis determinism (as first described by Epicurus), Sorabji thinks Aristotle's position on the question is clear enough. Voluntariness is too important to fall before theoretical arguments about necessity and determinism.

I come now to the question of how determinism is related to involuntariness. Many commentators nowadays hold one or more parts of the following view. Determinism creates a problem for belief in the voluntariness of actions. Regrettably, but inevitably, Aristotle was unaware of this problem, and so failed to cope with it. Indeed, the problem was not discovered until Hellenistic times, perhaps by Epicurus, who was over forty years junior to Aristotle, and who reached Athens just too late to hear his lectures. In Aristotle's time no one had yet propounded a universal determinism, so that he knew of no such theory. His inevitable failure to see the threat to voluntariness is all the more regrettable in that he himself entertained a deterministic account of actions, which exacerbated the problem of how any could be voluntary. I shall argue that this account misrepresents the situation.

First, Aristotle is aware of the idea that everything is determined, whether causally or non-causally. He considers a non-causal determinism in Int. 9, and a causal determinism not only in Metaph. VI 3, but also in Phys. II 4, where he remarks that some people had denied that there was such a thing as chance, on the grounds that a cause could always be found for everything (195b36 — 196a11). Admittedly, he takes the falsity of determinism as fairly obvious in Metaph. VI 3, and feels little need to discuss it in NE III, or in GC II 11. Indeed, in the last passage he asks whether all coming to be is necessary, but whether any is. None the less, he does sometimes produce arguments against determinism (Int. 9, 18b26 — 19a22; Phys. II 5, 196b14; GC II 11, 337b3-7). And he also thinks that in the light of its falsity, he needs to do some explaining, and to show how there can be events without a cause (accidental conjunctions, Metaph. VI 3), or how some predictions can avoid being already true
(Int. 9, 19a22—b4, on the traditional interpretation).

What Aristotle failed to discuss was not determinism, but something that William James was later to call 'hard' determinism,' the view not only is determinism true, but that also, because of it, there is no thing as moral responsibility or voluntary action. The commentators mentioned above are right insofar as they only want to say this. But what is debatable is whether we should see Aristotle's silence about `hard' determinism as simply a failure to see a problem, and how far the subsequent Hellenistic period differed from Aristotle in their readiness to discuss 'hard' determinism. Determinists in antiquity did not make it a triumphant conclusion that all actions are involuntary. Rather, they would have thought it an objection to their view, if they had to banish voluntariness. There is a whole battery of arguments, which turn up in treatise after treatise, urging against determinism, that it would do away with many of our conceptions about conduct and morality. In the De Fato of Alexander of Aphrodisias (fl. c. A.D. 200), where many of these arguments are used, it becomes clear that the Stoics, against whom they were directed, replied not by conceding the point, but by urging that fate did not exclude the standard moral concepts (chs 13-14, 33, 35-8 Occasionally, they seem to have gone over to the offensive, and argued like certain modern philosophers,5 that the standard moral concepts actually presuppose determinism. But... they felt little attraction towards 'hard' determinism, even if their founder Zeno (fl c. 300 B. C.) deployed an argument in an ad hominem way which is used also by hard determinists, that our moral practices are inevitable, whether justifiable, or not (Diogenes Laertius 7 1 23). Most ancients would have said, and so would Aristotle, that, if there is a genuine incompatibility between determinism and voluntariness, this is so much the worse for determinism, not for voluntariness; and even in modern times, 'hard' determinism is much rarer than 'soft'.

Aristotle himself, so far from failing to observe any incompatibility between determinism and our ordinary ways of thinking about conduct, actually tended to see such incompatibilities too readily. Moreover, so far from his successors starting a new tradition, they are often simply echoing Aristotle's own comments, when they argue that there is an incompatibility, and that it counts against determinism. We have seen that Aristotle thinks voluntariness incompatible with an action's having all along been necessary, and further that he goes so far as to argue (wrongly) against determinism that it is incompatible with the efficacy of effort or deliberation (Int. 9, 18b31-3, 19a7-8). This latter was echoed in one of the famous named arguments of antiquity, the Lazy Argument, according to which belief in determinism would make us lazy. A related argument, which we have already noticed, appears in NE II 5 (1113b21-30), where Aristotle claims (again wrongly) that since punishment and honours influence conduct, good and bad conduct must be up to us. Aristotle may here have been ignoring, rather than answering, the idea that wicked conduct is determined, and may have been concentrating instead on the point that our conduct is in some way dependent on us. But his successors used arguments like this one in order to attack determinism, and he too might have been willing to use the argument against a determinist, if he had felt himself to be confronted by one. Aristotle often repeats that we do not deliberate about what is necessary (NE III 3, 1112a21-6; VI 1, 1139a13; VI 2, 113967-9; VI 5, 1140a 31—b1; VI 7, 1141b10-11; III 3, 1112a30-1 with III 5, 1113b7-8; EE II 10, 1226a20-30; Rhet. I 2, 1357a8), and only once comes at all close to adding the desirable qualification 'unless we do not realise that such and such a course is necessary'. If determinism is incompatible with deliberation, it will also be incompatible with praxis, the distinctively human kind of action, and with moral virtue, both of which presuppose deliberation. Similar views on the relation of deliberation to determinism reappeared among Aristotle's ancient and modern successors. And they also turned against determinism the comment, which Aristotle makes in another context, that we cannot bestow praise and blame for what happens of necessity (NE III 5, 1114a23-9; EE II 6, 1223a10; II 11 1228a5), although we can bestow honour, e.g. on the gods (NE 1101b10 — 1102a4).

Those who think that determinism endangers voluntariness have every right to disagree with Aristotle's view that our ways of thinking about conduct endanger determinism. But they should recognise it as an alternative view. It misrepresents the situation to suggest that Aristotle was merely not yet in a position to appreciate the problem; he would not have agreed that the problem was one for believers in voluntariness. And the succeeding age would have supported him.
(pp. 243-6)

R. W. Sharples

Sharples' great translation and commentary Alexander of Aphrodisias On Fate appeared in 1983. He described Alexander's De Fato as perhaps the most comprehensive treatment surviving from classical antiquity of the problem of responsibility (τὸ ἐφ’ ἡμίν) and determinism. It especially shed a great deal of light on Aristotle's position on free will and on the Stoic attempt to make responsibility compatible with determinism.

Sharples thinks that the problem of determinism and responsibility was not realised, in the
form in which it was eventually passed on to post-classical
thinkers, until relatively late in the history of Greek thought - at least not until after Aristotle.

Although there are passages in which it is recognised that there is something problematic in holding someone responsible for an action that a god has foretold he will perform, it is generally misleading in the interpretation of the literature of the fifth century B.C. and earlier to assume that the difficulty is always as obvious or as important as it seems to us. The mechanistic atomism of Democritus (born 460-457 B.C.) may well seem to us to raise difficulties for human responsibility, and it seemed to do so to Epicurus, but Democritus himself apparently felt no such problem. The question of the relation between destiny and human choice is raised, in mythical form, at the end of the Republic of Plato (c. 429-347B.C.), in a passage that was to be important for later discussion; but it only attains its full significance in the context of a theory claiming that all events in the physical world are governed by a rigid determinism, and this is not present in Plato, for whom what admits of absolute regularity with no exceptions is to be found among the Ideas rather than in sensible phenomena.

The classic notion of determinism — of a system in which every state of affairs is a necessary consequence of any and every preceding state of affairs — is almost entirely absent from the approach to the physical world of Aristotle (384-322 B.C.) also; more important for him is the contrast between, on the one hand, the absolute necessity and invariance which applies to the motions of the heavenly bodies, to mathematical truths, and to certain attributes of beings in the sublunary world — the mortality of all men, for example — and, on the other hand, the irregularity and variation of many aspects of the sublunary world, where the most that can be said of many things is that they happen for the most part but not always, and where there are many accidental connections that fall outside the scope of scientific knowledge — concerned with what is always or usually the case — altogether.

Aristotle's picture of the consequences of an event is not one of chains of cause and effect interwoven in a nexus extending to infinity...Aristotle can assert that there are fresh beginnings (archai), not confined to human agency, without supposing that there is a deterministic causal nexus occasionally interrupted by undetermined events; he simply does not see the question in these terms. He does discuss the question whether all events are determined by necessary chains of causation at Metaphysics E 3 1027a30 — b14, and there denies this possibility insisting that not everything is necessary; but here as elsewhere it is not clear that he distinguishes between (i) the claim that there are events which are not predetermined, and (ii) the lesser claim that there are some things that do not always happen in the same way — which does not exclude their being predetermined by different factors on each occasion. He certainly holds that there are events which result from chance rather than necessity; but as has often been pointed out his treatment of chance events in terms of coincidence is not incompatible with determinism. He is in fact interested in a different question, that of explanation; it may well be that chance events have no scientific explanation, without their thereby involving indeterminism. It would indeed be rash to claim that there are no passages where Aristotle intends to assert freedom from determinism as later philosophers would understand it; but this is not, in dealing with the universe as a whole, his main concern. And Aristotle's emphasis on other questions, particularly that of the presence or absence of a variation which may well be entirely predetermined, was highly influential on later thinkers, Alexander among them, who were concerned with the problem of determinism.

Aristotle did however discuss the issue of the analysis of responsible human action in a way which, although it does not form part of a treatment of determinism in the world as a whole, was nevertheless to be influential when this topic was later discussed. In Nicomachean Ethics III.1 he defines voluntary (hekousion) action as that where there is no external compulsion, so that the source (arche) of the action is in the agent, and where the agent is not ignorant of the particular details of what he is doing. In this chapter he is concerned with the practical, quasi-legal problem of the imputability of actions to their agents, rather than with a philosophical analysis of freedom of choice, but the question of the presence or absence of external compulsion was to be important in later discussion.

In Nicomachean Ethics III1.5 Aristotle asserts that responsible actions — those which 'depend on us' — involve the possibility of choosing otherwise (1113b7). He then meets the objection that a man's character may be such that he cannot choose other than actions of a particular sort by arguing that, since dispositions develop as a result of actions, even if a man cannot now choose not to act in a certain way, it is his responsibility that he came to be like this in the first place (1114a3-31). This argument, however, only pushes the problem back into the past, till one comes
to influences in our childhood — natural endowment, training and education — for which we can hardly be regarded as responsible.

Aristotle is not indeed arguing against the background of a determinist system, and it would be a mistake to press his argument too closely so as to extract deterministic implications from it. It seems that he is operating with basically libertarian assumptions, starting from the position that responsibility involves freedom to choose between different courses of action, and dealing with difficulties arising from the determination of action by character only as a subordinate issue. It is true that 'the possibility of choosing otherwise' could be interpreted in a qualified sense which would make it acceptable to a determinist, but there is no explicit indication of this in Aristotle's text, and it seems likely that such ,attempts to reconcile determinism and responsibility only arose later as a reaction to the explicit assertion of the necessity of choosing between determinism and indeterminism. However, Aristotle's treatment is not entirely satisfactory, and its limitations and difficulties do become apparent when later thinkers, and above all Alexander, use it as a basis from which to argue against determinism.

It is with Epicurus and the Stoics that clearly indeterministic and deterministic positions are first formulated. Epicurus (341-270 B.C.) claimed that human freedom could only be maintained in the atomist system by the unpredetermined swerve of certain atoms from the paths which they would otherwise follow.

This is a misreading of Epicurus by his opponents that is still popular today

The problems of this position, which seems to reduce responsible human choice to pure randomness, have often been pointed out; however, analogous problems seem involved in any attempt to treat responsibility in terms of the possibility of choosing otherwise, if this is to be combined with a rational explanation of why men do, or should, choose in a particular way.

The Stoic position, given definitive expression by Chrysippus (c. 280-207 B.C.), the third head of the school, represents not the opposite extreme from that of Epicurus but an attempt to compromise, to combine determinism and responsibility. Their theory of the universe is indeed a completely deterministic one; everything is governed by fate, identified with the sequence of causes; nothing could happen otherwise than it does, and in any given set of circumstances one and only one result can follow — otherwise an uncaused motion would occur. Fate is also identified with providence and with god, and thus with pneuma or spirit, the divine active principle — or perhaps better the instrument or vehicle of the divine will — which penetrates the entire universe, bringing about and governing all processes within it and giving each thing its character.

Chrysippus was however concerned to preserve human responsibility in the context of his determinist system. His position was thus one of 'soft determinism', as opposed on the one hand to that of the 'hard determinist' who claims that determinism excludes responsibility, and on the other to that of the libertarian who agrees on the incompatibility but responsibility by determinism. The Greek to eph' hemin, 'what depends on us', like the English 'responsibility', was used both by libertarians and by soft determinists, though they differed as to what it involved; thus he occurrence of the expression is not a safe guide to the type of position involved. The situation is complicated by the fact that the debate is in Greek philosophy conducted entirely in terms of responsibility (to eph' hemin) rather than of freedom or free will; nevertheless it can be shown that some thinkers, Alexander among them, have a libertarian rather than a soft-determinist conception of responsibility, and in such cases I have not hesitated to use expressions like 'freedom'. The expression 'free will' is employed in discussions of the problem in ancient Latin writers.

Chrysippus argued that we are responsible for those actions which, even though they are predetermined, depend chiefly on ourselves rather than on external factors.

Again the misinterpretation of Epicurus

(Epicurus, by contrast, insisted that free actions must be free not only from external necessity but also from necessitation by factors internal to the agent).

Certain ancient authors put forward arguments for praise, blame, punishment and reward in a determinist system with no appeal to responsbility — arguments which may therefore be classified as hard determinist. The wrongdoer should be punished for the protection of others whether or not he is responsible for his actions, just as noxious plants or animals are destroyed. A Stoic source for these
arguments cannot be ruled out, for the Stoics may well have reinforced soft-determinist arguments justifying praise, blame, punishment and reward by others not referring to responsibility.

In addition to physical, causal determinism one may also speak of 'logical' determinism. In chapter 9 of his De Interpretatione, the famous 'Sea-Battle' passage, Aristotle poses the problem that, if a prediction is either true or false, it seems that what is predicted must in the one case necessarily occur and in the other necessarily not occur. Aristotle's own solution to the problem is obscure. Both Epicurus and the Stoics accepted a connection between the truth or falsity of the prediction and the eventual outcome's being predetermined, Epicurus rejecting determinism and consequently denying that all future-tense propositions are true or false, the Stoics arguing that all propositions are true or false and using this as an argument to support determinism. Carneades (214/3-129/8 B.C.), the founder of the sceptical New Academy, argued against both schools that the necessary connection between the truth of the prediction and the occurence of the event is simply an indication of what is meant by describing a proposition as true, and does not have any deterministic implications. The predominant interpretation of Aristotle's own position in later antiquity was that a prediction of a future contingent event does have a truth value — it is true or false — but not a 'definite' one," this position first appears in the last section of quaestio 1.4 attributed to Alexander, but is not found in the de fato. It was probably advanced as a defence against those who attacked Aristotle as denying that predictions of contingent events had any truth value at all; Cicero indeed attributes this position to Epicurus and not to Aristotle (whom he regards as a determinist), but we know that both Stoics and others had attacked Aristotle for holding such a view.

A form of logical determinism which the Stoics however found less acceptable was that involved in the Master Argument of Diodorus Cronus (fl. c. 315-284 B.C.), a member of the Dialectical school.From the premisses 'all that is past and true is necessary' and 'what is impossible does not follow from what is possible,' Diodorus claimed to infer that only what is, or will be, true is possible. Both Chrysippus and his predecessor Cleanthes (331-232 B.C.), however, rejected this conclusion, Cleanthes rejecting the first premiss, Chrysippus the second. For the Stoics there are things that are possible even though they will not happen and even though it is predetermined that they will not. Nevertheless, Cicero (106-43 B.C.), in his de fato, and other anti-determinist critics of the Stoics claimed that this was not compatible with their determinist position, and that they were committed to Diodorus' definition of the possible whether they liked it or not. The issue is really one of the point of view taken. Even in a determinist system it may be useful to distinguish between things which could happen (given certain circumstances) but may or may not actually do so, depending on factors which may be obscure to us, and others which cannot happen at all. But those who are opposed to determinism are likely to find all such distinctions beside the point as long as it is still admitted that the actual outcome in each case is predetermined.

Cicero's treatise, of which unfortunately only the later part is extant, apart from a few fragments, is of particular importance for its presentation of the arguments advanced by Carneades, from whom the greater part of the treatise seems ultimately to derive. Just as in the case of the problem of the truth of predictions Carneades endeavoured to show that both the Stoic and the Epicurean position rested on a common misconception, so in the case of physical determinism he argued that there was a middle ground between universal determinism on the one hand, and the occurrence of uncaused events on the other. Chance events are caused, in that they have accidental causes, but not predetermined; human actions are not uncaused because their cause is in the nature of voluntary motion itself. Both these claims are similar to ones made by Alexander.

It was probably Carneades, too, who made popular a series of arguments from the alleged practical consequences of determinism, reflected in later authors and among them Alexander (f. XVI-XX). Our information on the place of Carneades in this tradition would probably be much better if we still possessed the lost part of Cicero's de fato.

As to the thought of Alexander himself, Sharples notes that in his attack on the Stoics Alexander does not name any individual thinkers and makes his arguments very general.

Alexander throughout speaks as if fate and necessity, for the determinists, were identical; the Stoics may indeed have been prepared in certain contexts to say that all things were necessary, but it does not seem that they laid such emphasis on the necessity of all things as does Alexander in stating his opponents' position. But since Alexander finds his opponents' attempts to separate fate and necessity trivial, from his own point of view his presentation of the determinist position is legitimate. It follows, however, that his statements must be used with considerable caution as evidence for the Stoic position.

Alexander's own position becomes apparent not only in the constructive argument of de fato but also in his polemic against the determinists, though the structure of his treatise has the consequence that his own position is not always clear — his arguments against the determinists are often dialectical, and he is concerned to refute them on diverse topics rather than to construct a systematic position of his own.

One crucial point that is however clear is that Alexander's own conception of responsibility is a libertarian one. He objects not just to determination of our actions by external causes alone, but to that resulting from a combination of internal and external factors; it is not enough that an individual contributes something to the result, if that contribution is predetermined. This shows that his repeated descriptions of responsbility in terms of the power or capacity for opposite courses of action"' are to be understood in terms of an unqualified, unrestricted possibility. At the same time, like Carneades, he claims to avoid the Stoic charge of introducing uncaused motion. Epicurus is nowhere mentioned in the de fato in connection with determinism, but only with reference to his denial of divine providence; possibly consideration of the Epicurean atomic swerve would have exposed difficulties in Alexander's own position. He stresses the connection between responsibility and reason, which shows that his libertarian conception of responsibility is not just one of arbitrary caprice; at the same time, he faces very real difficulties in combining his libertarian position with an account of the rational element in human behaviour, and does not really solve it. (For the Stoics and Neoplatonists, on the other hand, freedom is located not in the possibility for alternatives but precisely in choosing the most rational course of action.)'"

Don Fowler

In his 1983 thesis, "Lucretius on the Clinamen and 'Free Will'," Fowler criticized Furley's limits on the swerve and defended the ancient - but seriously mistaken - claim that Epicurus proposed random swerves as directly causing our actions. This mistaken claim has become common in current interpretations of Epicurus.

[The discussion of the swerve in Book II of De rerum natura] has received brilliant treatment from D. J. Furley in a work which is in many ways a model for the analysis of ancient philosophical texts. Yet it still seems to me that there is more to be said. I want here to try briefly to offer a fresh analysis of the argument of the vital paragraph 251-93, and to situate it within an Epicurean context. Inevitably this will involve criticism of Furley; let me state again at the outset my admiration of his work.
("Lucretius on the Clinamen and 'Free Will'", Συζήτησισ: Studi sull'epicureismo greco e romano offerti a Marcello Gigante, (Naples, 1983), p.330)

(The thesis is reprinted as Appendix A in Lucretius on Atomic Motion, 2002, p.407)

I turn to the overall interpretation. Lucretius is arguing from the existence of voluntas to the existence of the clinamen; nothing comes to be out of nothing, therefore voluntas must have a cause at the atomic level, viz. the clinamen.

This is not an interpretation that would have been acceptable to Epicurus

The most natural interpretation of this is that every act of voluntas is caused by a swerve in the atoms of the animal's mind. The σημείωσις of L. 2. 125-41 is exactly parallel; the visible motions of the dust-particles are a σημεῖον [ἀπὸ τῶν φαινομένον] (128 significant) for the invisible atomic motions which are their cause. There is a close causal, physical relationship between the macroscopic and the atomic. Furley, however, argued that the relationship between voluntas and the clinamen was very different; not every act of volition was accompanied by a swerve in the soul-atoms, but the clinamen was only an occasional event which broke the chain of causation between the σύστασις of our mind at birth and the 'engendered' state (τὸ ἀπογεγεννημένον) which determines our actions.

Epicurus would not want actions that are "up to us" to be randomly caused

Its role in Epicureanism is merely to make a formal break with physical determinism, and it has no real effect on the outcome of particular actions.
(p.338)

For Furley, both of these accounts are essentially ones of stimulus and response; action follows automatically upon perception, and the nature of the action is determined by our constitution, the sort of person we are. In accordance with this, he analyses the passage from De rerum natura Book 4 as follows:

(1) Simulacra meandi must strike our minds, among the innumerable other simulacra which are always abroad in the air (881-885).

(2) The mind must be focussed, as it were, on walking, so that these simulacra form an image while others do not (882-886).

Here the occurrence of voluntas is consequent on the focusing of the mind. But that is not what Lucretius says; a more accurate analysis of the paragraph would be:

(1) 881-2. First simulacra strike the mind, as explained previously.

(2) 883-5. Next voluntas occurs; for the mind does not begin any action before the process of 'prevision' has taken place. An imago is formed of what the mind anticipates.

(3) 886-90. Therefore, when the animus moves itself in such a
way as to want to go, straight away it transmits its motion to the anima. Then the anima strikes the body . . .

Lucretius is concerned in this passage with how we move when we wish to, not with how we come to wish to move; hence there is no explanation of how voluntas occurs. But there is certainly no evidence for the idea that voluntas is caused by sense perception directly, and hence that there is no room for the occurrence of a clinamen in the soul-atoms. Simulacra are striking our mind all the time, but we do not 'see' them unless we concentrate on them in an ἐπιβολή τῆσ διανοίας, as Lucretius explains in 4. 802-17. What we concentrate on depends on our voluntas. Once the image is clearly visualized — once we have a φαντασία — then indeed the bodily reactions proceed from that automatically. But voluntas comes before, not after, the production of the image; as K. Kleve remarks, 'wir können selbst wählen, welche Bilder wir bemerken wollen, d.h. auf welche Bilder wir unsere Aufmerksamkeit (ἐπιβολή) richten wollen'. Furley argues that we cannot situate voluntas at this stage 'because Lucretius goes to great lengths to give a causal explanation of why the mind focuses on some things rather than others'. The passage
referred to is 4. 962-1036, and in particular 973-83. But Lucretius is clearly there describing an exceptional and involuntary experience which offers an analogy for the phenomenon of dreaming. There is no suggestion that that is what ordinary perception and thought, still less action, are like.

For Furley, Epicurus' clinamen is only an occasional event which breaks the chain of causation. So voluntas might be an agent-causal will that is "up to us".

There is therefore no reason to doubt that in 4. 881-90 Lucretius situates voluntas before the act of ἐπιβολή and therefore no reason to see voluntas as causally conditioned by perception. Ample room is left for the clinamen to fill; and indeed what else could fill it?
(p.341)

For Lucretius, voluntas takes place in the mind, the animus, but it is also a purely
physical occurrence. There is no disembodied faculty of the will separate from the physical constitution of the animal." Voluntas is not, moreover, in Lucretius' view merely the object of introspection; we can see it occurring in others. It takes place when the mind decides to focus on certain simulacra in an ἐπιβολή τῆσ διανοίας, and is thus situated between sense perception and the formation of a specific φαντασία which leads to action. It is caused by a random swerve in the downward motion of an atom or atoms in the 'fourth substance' of the animus, which causes an alteration in the atomic motions which eventually leads to a specific action. What action, if any, a swerve issues in is determined by which atoms swerve and by the constitution of the animus. On any particular occasion, what action the animal will take is unpredictable, but over a series of actions his reactions to the external world will be broadly consistent with the sort of being he is. This theory has usually been greeted with contempt, in ancient and modern times. And its special problems are undoubtedly immense, quite apart from those which face any traditional account of the will as a distinct psychological phenomenon. But it is also a bold imaginative scheme, and an attempt to produce a precise physical account of puzzling psychological problems; it is surely, other considerations apart, a more interesting theory than a mere rehash of Aristotelianism would have been, however philosophically more respectable. It was not the whole of Epicurus' answer to the problems of human freedom; I have not touched at all on Epicurus' denial of a truth-value to statements about the future, which was designed to refute logical determinism as the clinamen did physical. The relationship between this move and the introduction of the clinamen is not clear, and requires further study. But I hope I have shown that the theory of the clinamen as presented by Lucretius is a self-consistent, reasoned theory
in itself, firmly embedded in the Epicurean system as a whole and designed to answer real philosophical problems, rather than merely an awkward embarrassment.
(p.351-2)
(Don Fowler, "Lucretius on the Clinamen and 'Free Will'", Συζήτησισ: Studi sull'epicureismo greco e romano offerti a Marcello Gigante, (Naples, 1983) 329-52)

A. A. Long and D. N. Sedley

In their great 1987 work The Hellenistic Philosophers (dedicated to David Furley), Long and Sedley discussed Epicurus and the free will problem at length, with references to the principal original Greek and Latin sources. (Long and Sedley did for the Hellenistic philosophers what Diels-Kranz did for the Pre-Socratics. Letter references below are to the fragments in Long and Sedley volume 2. Number references are to sections of volume 1.)

Epicurus' problem is this: if it has been necessary all along that we should act as we do, it cannot be up to us, with the result that we would not be morally responsible for our actions at all (especially A, E 3, F 1, G). Thus posing the problem of determinism he becomes arguably the first philosopher to recognize the philosophical centrality of what we know as the Free Will Question. His strongly libertarian approach to it can be usefully contrasted with the Stoics' acceptance of determinism (see 62).

Epicurus certainly saw the Democritean atomism which he had inherited as vulnerable to such a challenge, since it made all phenomena, including human behaviour, fully accountable in terms of rigid physical laws of atomic motion, and hence necessary: see A 2, C 13-14, E 3, G. It is perhaps the most widely known fact about Epicurus that he for this reason modified the deterministic Democritean system by introducing a slight element of indeterminacy to atomic motion, the 'swerve' (on which see also 11H with commentary): E 2-3, F, G. But taken in isolation such a solution is notoriously unsatisfactory.

It promises to liberate us from rigid necessity only to substitute an alternative human mechanism, perhaps more undependable and eccentric but hardly more autonomous. Epicurus' remarks in A 1, where 'that which depends on us' (or 'that which is up to us') is contrasted with unstable fortune as well as with necessity, suggest that he meant to avoid this trap. In order to see how, we must defer discussion of the swerve for now..

Given today's quantum mechanical indeterminacy, Epicurus' intuition of a fundamental randomness in nature was correct. But he did not think the swerves were the direct causes of our actions. He agreed with Aristotle that beyond necessity (άνάyκη) and chance (τυχῆ), there is a third kind of basic cause - agent causes (ἐφ' ἡμῖν or παρ’ ῆμᾶς). How exactly determinism and chance relate to autonomous agent causality is not made clear, but Aristotle and Epicurus should be classed today as "agent-causal libertarians."

The swerve is not even mentioned in the surviving papyrus fragments [B,C] of Epicurus' book on the issue of responsibility from which B and C are drawn But the book still sheds abundant light on the question. In C he conducts a running debate with a Democritean determinist. Democritus himself, we are told, simply failed to see the implications of his determinism for human action (C 13-14). Epicurus' principal target in C 2-12, on the other hand, is someone who consciously applies mechanistic determinism to all human behaviour, including his own. He probably has in mind such fourth-century Democriteans as his own reviled teacher Nausiphanes — the heirs of Democritus derided C 13, as perhaps also implicitly in G. (The early Stoics have sometimes been identified as his target, but cf. 62 with commentary; 'natural philosophers', A 2. would not normally be used of Stoics, in any case.)

In C 1 Epicurus is arguing that since we start with a wide range of potentials ('seeds') for character development our actual direction of development is not physically predetermined but 'up to us'. There are physical influences, but we can control them (cf. 15D 7-8). If it were they that controlled us, our moral and critical attitudes to each other would make no sense (C 2). This leads him into his anti-determinist digression, which continues until its express conclusion at C 15. The determinist may simply regard these attitudes as themselves necessitated (C 3). But this does not save him from the charge of self-refutation (C 5, and perhaps already in the very fragmentary C 4): his own critical attitude in this very debate still implies what he wishes to deny, that the parties to the debate are responsible for their own views. The determinist will resort to the defence that he is compelled to behave in this way; when challenged once again for continuing to argue, will repeat the defence; and so on ad infinitum. Epicurus' objection to this infinite regress (C 6) is not that it is in itself vicious, but rather that it leaves the inconsistency untouched: at every stage of the regress the determinist's behaviour in continuing to argue his case as if with a responsible agent contradicts his thesis that everything, including our beliefs, is mechanically necessitated.

In the second stage of the digression, C 8-12, Epicurus suggests that determinism cannot amount to a substantive thesis about the world, and that its application of 'necessity' to human agency will turn out to be no more than a change of terminology. First (C 8) comes an appeal to 'preconception' (on which as a criterion, see 17 above). We all share a preconception of our own agency as that which is responsible for our behaviour: to defuse the evidential force of this, the determinist would have to show how the alleged preconception has come to embody a faulty 'delineation' (cf. 17E 2, 5) of the facts. (Compare Epicurus' own grounds for dismissing the alleged preconception of the gods as provident, 23B—C below.) If he cannot, the preconception remains valid and the determinist's contribution is merely a new name for it. Second (C 9), his thesis is pragmatically empty. Since he denies us an internal source of self-determination (an 'auxiliary element or impulse in us') he can never expect his arguments to dissuade us from any action. In this Epicurus contrasts him with someone who has a proper grasp (as recommended in A 1) of the difference between the necessitated and the unnecessitated, and who consequently can expect to dissuade us from actions which would involve resisting necessity (C to) perhaps, for example, dissuade us from a vain desire to evade the inevitability of death, because unlike the determinist he can appreciate that while death is necessary our wishes are up to us. Third (C II), the determinist leaves himself no tools for analysing 'mixed' actions (as they are called by Aristotle, Nicomachean ethics in. I), those performed freely but reluctantly in avoidance of a greater evil, since he is unable to distinguish the voluntary from the necessitated elements in them.

The final stage of the argument, C 13-14, is pragmatic, appealing to the disastrous practical consequences that would have ensued had Democritus remembered to apply his thesis of universal necessitation to himself. No illustration is given, but one easy example would be the abandonment of decision-making (cf. 55S).
It is remarkable how closely the internal structure of this anti-determinist argument matches that of 16A's anti-sceptic argument, with the sequence of a self-refutation challenge (C 3-7; cf. 16A 1), an appeal to preconception and word-meaning (C 8-12; cf. 16A 2-3), and a pragmatic argument (C 13-14; cf. 16A 9-10). So too its function as a digression added late in the book to justify the preceding positive account of psychological causation matches the role of 16A in relation to Lucretius' preceding positive account of sense-perception. None of this is likely to be mere coincidence. For scepticism and the kind of mechanistic determinism envisaged here were seen as joint consequences of Democritus' reductionist atomism. If phenomenal properties were reducible to mere configurations of atoms and void, it seemed to follow that the atoms and void alone were real while the sensible properties were arbitrary constructions placed upon them by our cognitive organs. The result was scepticism about the sensible world, which had become the characteristic stance of most fourth-century Democriteans (see further, 1 and 16). Similarly, if the 'self' and its volitions were reducible to mere sequences of atomic motion in the soul, human action would easily appear to be mechanistic, fully explicable in terms of primary physical laws, with no additional explanatory or descriptive role left for such psychological entities as belief and volition. And that is just the kind of theory under attack in C (cf. especially C 2, 9).

Given the extent of this parallelism between scepticism and determinism, and between Epicurus' respective refutations of them, we might expect his own positive alternatives to them to be similarly comparable. And so they are.

Just as his answer to scepticism is to affirm the reality of phenomenal properties and the truth of sense-impressions of them (see on 7 and 16), so too his answer to mechanism is to affirm the reality and causal efficacy of the self and its volitions as something over and above the underlying patterns of atomic motion. This plainly emerges from B, despite the lack of context and certain difficulties of interpretation. Epicurus is speaking of self-determining animals. (Volitional autonomy is not restricted to human beings, cf. F 1-2; but elsewhere in the book, j in vol. 2, wild animals seem to be excluded, as lacking self-determination and hence as exempt from moral criticism, though not from hate.) Their misbehaviour is quite explicitly said (B 1-4) to be attributable not to their atoms but to their selves and their 'developments'. The latter term, which is crucial to the entire book's discussion, is explicated at B 5. The kind of 'development' which contributes psychological autonomy is one which is distinct from the underlying atoms in a 'differential' way ('transcendent' would be a tempting translation of the Greek word) — a way more radical than 'the way which is like viewing from a different distance'. The point is apparently that all bodies have certain properties, e.g. colour, over and above their constituent atoms, but that there the main difference is one of scale, one between macroscopic and microscopic analysis; whereas the 'developments' which supply autonomy differ from the atoms in a much more fundamental way. The fragmentary state of the text leaves us to guess at the nature of this difference, although it is hard to doubt that it includes the intentional properties associated with consciousness. How do these psychological entities relate metaphysically and causally to the mind's atoms? They can only be, technically speaking, 'accidental attributes' of those atoms (cf. 7). But they are not mere epiphenomena, supervenient on atomic motions and causally determined by them. For Epicurus is quite explicit in attributing to them a causal efficacy distinct from that of the atoms. Hence, although atomic make-up may be responsible for disorderly motions of the mind-atoms (B 4), it does not follow that we cannot make decisions which override those motions, and according to B 6 psychological causation actually operates on our component atoms. This throws immediate light on Lucretius' insistence at 14D 5 that although atomic composition of the soul determines our natural temperament, we can learn through reason to overcome that temperament. Perhaps, for instance, a natural coward can learn courage through rational reflection. His disorderly motions of soul atoms may then be stabilized, so that he ceases to suffer even the physical sensations of fear.

By now the familiar 'materialist' label is beginning to fit Epicurus less neatly. Although he holds prima facie an Identity Theory of mind (see 14), he does not regard mental states as capable of straightforward physical analysis, for although properties of the corporeal mind they are not mere physical states of it. We have here, then, an interactionist dualism of the mental and the physical. But there is no hint of Cartesian dualism. A better comparison would be with the modern notion of Emergence. In Epicurus' view, matter in certain complex states can take on non-physical properties, which in turn bring entirely new causal laws into operation.

B 7 emphasizes that the distinction between physical and psychological causation is crucial to an understanding of responsibility. And certainly it does constitute at least the beginning of an answer to determinism. The 'self' which is responsible for our actions is, Epicurus will say, more than a mere bundle of atoms, and therefore is not reducible to a link in a physical causal chain. Indeed Carneades, in defending Epicurean libertarianism for his own dialectical purposes (see 70G and commentary), suggested that this was already a sufficient answer to determinism: E 4-7. But how, it will be asked, can this emergent property of the corporeal mind so effectively take control of the soul, and through it of the body, as to move their atoms in ways in which according to the laws of physics alone they should not have moved? If the laws of physics are sufficient to determine the precise trajectory of every atom in us, how can the self be anything more than a helpless spectator of the body's actions?

Here at last a significant role for the swerve leaps to the eye. For it is to answer just this question, according to Cicero at E 3, that the swerve was introduced. The evident power of the self and its volitions to intervene in the physical processes of soul and body would be inexplicable if physical laws alone were sufficient to determine the precise trajectory of every atom. Therefore physical laws are not sufficient to determine the precise trajectory of every atom. There is a minimal degree of physical indeterminism — the swerve. An unimpeded atom may at any given moment continue its present trajectory, but equally may `swerve' into one of the adjacent parallel trajectories (see commentary on 11H).

As far as physics is concerned there is simply no reason for its following one rather than another of these trajectories. Normally, then, the result will be, in this minimal degree, random. But in the special case of the mind there is also a non-physical cause, volition, which can affect the atoms of which it is a property.

It does so, we may speculate, not by overriding the laws of physics, but by choosing between the alternative possibilities which the laws of physics leave open. In this way a large group of soul atoms might simultaneously be diverted into a new pattern of motion, and thus radically redirect the motion of the body. Such an event, requiring as it does the coincidence of numerous swerves, would be statistically most improbable according to the laws of physics alone. But it is still, on the swerve theory, an intrinsically possible one, which volition might therefore be held to bring about. For a very similar thesis relating free will to modern quantum indeterminism, see A. S. Eddington, The nature of the physical world (1928). (It may be objected that swerves are meant to be entirely uncaused; but, as E 2 shows, that was only an inference by Epicurus' critics, made plausible by concentrating on the swerve's cosmogonic function, cf. 11H, for there it must indeed occur at random and without the intervention of volition.)

Sedley here assumes a non-physical (metaphysical) ability of the volition to affect the atoms, which is implausible. But the idea that the volition chooses (consistent with and adequately determined by its character and values and its desires and feelings - from among alternative possibilities provided randomly by the atoms - is quite plausible.

Lucretius' evidence in F does not explicitly state the swerve's relation to volition, although numerous attempts have been made to discover it there. But if the above account of Epicurus' theory is justified by the other testimonia, it becomes clear that F is, at least, fully consistent with it. For the dominant theme of F 1-3 is precisely the evident power of volition to redirect the bodily mass in defiance of its purely mechanical patterns of motion. This is said, in F 1 and 4, to be explicable only if there is an undetermined swerve of atoms, since if impact and weight were the only causes of atomic motion the mind's behaviour would be rigidly mechanistic. Some have also seen in F 1 the further implication that the initiation of every new course of action directly involves the swerve. All this fits the above account comfortably enough. What is missing, of course, is an explanation of the non-physical character of psychological causation — not surprisingly, given that Lucretius' poem is about physics and that his sole object in the context is to complete his account of the laws of atomic motion (cf. 11).

One further dimension to the debate emerges from E 1, H and I. Epicurus saw the threat of universal necessitation not only in unbreakable chains of physical causation, but also in the logical principle of bivalence according to which every proposition is either true or false, including those about the future. His solution of denying the principle as far as certain future-tensed propositions are concerned (the denial is slightly garbled in I's version, where 'one or the other is necessary' ought to read 'one or the other is true'; but the example is clearly authentic — Hermarchus was Epicurus' pupil and successor) was essentially that of Aristotle, according to the traditional reading of his celebrated Sea Battle discussion at De interpretatione 9. But Epicurus, like the Stoic with whom he is contrasted in E I (see further, 38G), saw physical and logical determinism as two aspects of a single thesis. The two formulations of determinism tend to be treated as interchangeable, as do the two respective solutions, the swerve and the denial of bivalence (cf. Cicero, On fate 18-19, and perhaps E 1-3). This conflation seems to rest on the assumed equivalence of 'true in advance' with 'determined by pre-existing causes'; cf. also the telling comment at the end of I.

The interpretation of the swerve theory adopted above may help explain how it could be thought interchangeable with the denial of bivalance. Neither doctrine is involved in analysing the nature of volition itself (as many have thought the swerve to be). Their shared function is to guarantee the efficacy of volition, by keeping alternative possibilities genuinely open.
(Long and Sedley, The Hellenistic Philosophers, section 20, "Free Will," pp.107-112)

Walter Englert

In his 1987 book, Epicurus on the Swerve and Voluntary Action, Walter Ebnglert agreed with Furley that Epicurus did not introduce the swerve to explain "either free or deliberate choice, but rather to prevent human character from being rigidly fixed at birth." (p.3)

Englert argues that fundamentally Epicurus wanted to defend moral responsibility. Ironically, this is the same thing Democritus was trying to achieve with his idea of determinism, namely, to convince humans that they have the reponsibility, not gods arbitrarily interfering in human actions.

Earlier scholars have not thought it significant that our ancient sources differ in reporting what Epicurus was attempting to account for with the swerve. I have argued that the Lucretius passage presents Epicurus' analysis of how the swerve preserves τὸ ἐκούσιον, voluntary action, and Plutarch in one passage specifies τὸ ἐκούσιον as the reason Epicurus posited the swerve. But several other passages from Plutarch, Cicero, and Philodemus report that Epicurus sought to account for τὸ ἐφ’ ἡμῖv, τὸ παπ’ ἡμᾶς, and in nostra potentate with the swerve. All three expressions are equivalent and refer to the topic treated in the preceding chapter, τὸ ἐφ’ ἡμῖv "that which depends on us", or simply, "moral responsibility". I take it that for Epicurus, as for Aristotle, τὸ ἐκούσιον is the broader classification of which τὸ ἐφ’ ἡμῖv is a sub-class. All living creatures (including the horses in the Lucretius passage) can act voluntarily (τὸ ἐκούσιο), but only human beings are responsible for their actions (τὸ ἐφ’ ἡμῖv). What I will try to show in this section is how Epicurus, once he had developed the theory of the swerve and applied it to the problem of voluntary action, also made use of it in his defense of moral responsibility.
(Epicurus on the Swerve, p.129)

Epicurus, given his very different views about the nature of the universe, its physical structure, and the nature of the gods, could not take refuge as the Stoics did in divine providence. In the Letter to Menoeceus (section 134) he clearly states his view on necessity:

For, indeed, it were better to follow the myths about the gods than to become a slave to the destiny of the natural philsophers; for the former suggests a hope of placating the gods by worship, whereas the latter involves a necessity which knows no placation. (C. Bailey's translation)

Epicurus, who believed that the gods existed but took no interest in human affairs or in running the universe, could not, as the Stoics did, offer comfort to people by teaching that the world of which we are a part is ruled by the providence of a divine being.
(Epicurus on the Swerve, p.132)

If our actions are simply parts of a much larger causal nexus, the notion of τὸ ἐφ’ ἡμῖv, "what depends on us", becomes very problematical. On Epicurus' account our actions would not be part of an overall divine plan, but simply necessary events in what is ultimately analyzable as an atomic chain of causation. If true, in what sense could actions be up to us? How ultimately could we be sure that we can control our lives, and thus attain happiness?

Epicurus developed the means to avoid the alternative the Stoics preferred. Rejecting the theory of eternal chains of causation, and the principle of bivalence which he felt depended on it, he was able to maintain that τὸ ἐφ’ ἡμῖv and related terms used to express the concept of moral responsibility were meaningful. The main evidence for how he attempted to preserve moral responsibility is found in Cicero's De Fato, in Plutarch, and in the fragments from a book of Epicurus' On Nature.
(Epicurus on the Swerve, p.133)

Englert cites Cicero's understanding of Epicurus,

Nor, since these things are so, is there a reason for Epicurus to be so frightened at fate, and seek protection [sc. against fate] from the atoms, and lead them from their the path [= the swerve]...
(Cicero, De Fato, 18-19)

In the passage from the De Fato quoted above, Cicero relates that Epicurus introduced the swerve out of fear that without it the chain of causation would not be broken. Where does this break in causation occur? There seem to be at least two possibilities.

First, given his views on atomic motion, Epicurus could deny that anything, including the motions of inanimate and animate objects, is necessary in a strict sense. He maintained that any atom has the possibility of swerving at any time...Such an analysis gives Epicurus a plausible means of denying that the principle of bivalence holds true for future propositions and that all events are connected by a chain of causation, and may have allowed him to argue for the existence of chance in the universe, but it does not directly explain why he felt the swerve preserved moral responsibility.

This brings us to the second alternative, where his analysis of τὸ ἐφ’ ἡμῖv becomes crucial. The question of how τὸ ἐφ’ ἡμῖv was to be preserved in the context of this discussion focused primarily on one question: If the actions of human beings are analyzed as simply part of a larger causal chain, are they not caused, and therefore completely determined, by the external causes that precede them? In this context, a philosopher who wanted to show how our actions are τὸ ἐφ’ ἡμῖv had to demonstrate that they are not completely determined by external causes.
(Epicurus on the Swerve, p.133-34)

Englert says that Cicero made it clear that Epicurus's swerve was precisely to provide human freedom and responsability.

Epicurus introduced this theory [sc. of the swerve] for the following reason. He feared that, if the atom is always carried along by natural and necessary weight, nothing would be free for us, since the mind is moved as it is forced by the motion of atoms.
(Cicero, De Fato, 23)

...since swerves are random, it is hard to see how they help to explain free action. We can scarcely expect
there to be a random swerve before every free action. Free actions are frequent, and (fairly) reliable. Random swerves cannot account for either of these features. This problem would be lessened if we could assume that swerves are very frequent, so that there is always likely to be one around before an action. However, if swerves are frequent, we face the problem that stones and trees ought to be enabled to act freely. And even in the case of humans random swerves would seem to produce, if anything, random actions; we still lack any clue as to how they could produce actions which are free.

An influential modern line of thought avoids these problems by arguing that our evidence does not demand that there be a swerve for each free action [Furley]. Rather, swerves explain the fact that people have characters capable of change and reaction that goes beyond mechanical response to stimuli. We act freely because we have characters that are flexible and spontaneous, and this is because we are composed of atoms which swerve occasionally. On this account, swerves do not have to be frequent, since they are not part of any mechanism of action; one swerve in your soul is enough for the kind of character flexibility that is required. Such an account avoids the problems attaching to any account that brings swerves into free action, but at the cost of not answering very closely to the evidence; the Lucretius passage certainly suggests that swerves are in some way relevant at the point of action.

Another kind of suggestion is that swerves are not the causes of free actions at all. Rather, they come into the process whereby free actions are brought about. Swerves are supposed to explain something about the nature of free agency and how it works, but they do not cause free actions (by cutting across causal chains, for example). This suggestion can be developed in several ways. The boldest version holds that swerves do not explain the existence of free volitions at all; [Sedley] rather Epicurus holds anyway that volitions are nonphysical, "emergent" entities.

The role of swerves is to provide alternative possibilities for volitions to choose between, for there would be no point in having free will if there were no genuinely open possibilities between which to select. This suggestion depends on the strong thesis that Epicurus regards the mind as something nonphysical, which we have seen to be highly contentious; and also it likewise does not really answer to the evidence, in which it is not merely the possibility of swerves, but actual swerves, which play a role at the level of action. A second kind of account gives the swerve a role in enabling the mind to focus on one thing rather than another by way of the mind's selective "grasp" or epibole tes dianoias. A third sees it as parallel to Aristotle's use of the connate pneuma; that is, it creates a new kind of physical substance which explains, within a physicalist system, how human minds can be active, and in particular can initiate action.

It is undoubtedly more attractive to find a role for swerves in the mechanism of free action, rather than as mysterious events enabling free action to come about. However, all such accounts face the problem of evidence: Lucretius, the only source who gives us much detail about the swerve in human action, associates it with the formation of impulse (voluntas), not with any subsequent mechanism to carry it out. However embarrassing we may find the thesis that the swerve explains the formation of free impulses, and in some way explains how they are free, that remains the view best supported by the ancient evidence.

As we have seen, however, occasional random swerves cannot produce reliable free actions. The only way that the theory has a hope of working is on the assumption that swerves are extremely frequent, so as to produce a standing physical con
dition. How, though, do we avoid the obvious objection that trees and stones would also contain frequent swerves, given that it is an important aspect of Epicureanism that human beings are parts of nature, atomic compounds like the others? We can meet this objection by the consideration that swerves are indeed everywhere frequent, but that they produce effects only in human souls, perhaps indeed only in the rational parts of human souls. This is because the human rational soul is a compound of the finest and most tenuous atoms, and only this kind of compound permits swerves to have effects. Thus we are free, and trees are not, because of a physical difference: in our minds atomic swerves produce effects, which somehow enable us to act freely. While the mechanism remains somewhat sketchy, we can see the general idea. Swerves do not operate one per action; rather, because we (and some animals) are the kinds of atomic compound that we are, we are able to act freely, in a way that genuinely chooses between alternatives.

But now we find a striking redundancy, for Epicurus has already postulated the nameless atoms in the soul to account for the complexity of sentient and intelligent behavior. Why do we need swerves as well to account for the same fact? Impressive as the fact may be, we hardly need two such physical differences to account for it. It might be objected that nameless atoms account only for agency, while we need swerves to account for free agency. But it is quite unclear from our evidence what this difference would be taken to consist in. This is especially so since Lucretius uses animal behavior as an example of free agency, ruling out the otherwise promising idea that freedom might be a matter of informed choice between alternatives, or something similar which is plausibly found only in humans.

It is very hard not to feel pressured here toward a developmental hypothesis, namely, that Epicurus had both these ideas, but not at the same time. It has been suspected on other grounds that the swerve was a late idea of Epicurus', one developed after he had written his major works, possibly in response to objections. It is also possible that Epicurus himself had no very definite theory of how the swerve underpins free agency, and that later Epicureans filled in the story, possibly in divergent ways, just as modern scholars do. It is hard to conclude, however, that the swerve was a good idea, and the disproportionate emphasis which it has received in discussion of Epicurus' ideas about the mind has been unfortunate.
(Julia Annas, The Hellenistic Philosophy of Mind, pp.184-88)

Jeffrey Purinton

In a 1999 Phronesis article, Purinton agrees with Fowler that random swerves directly cause volitions and actions. The ideas of Furley and Fowler do not do justice to Epicurus' libertarianism, he says, "since they do not make volition itself a fresh start of motion, and Sedley's view does not do justice to his atomism...It seems to me, therefore, that there is no good reason to reject the thesis that Epicurus held that swerves cause volitions from the bottom up. And there are a number of good reasons to accept it."

Purinton makes the all-too-common common error of translating Lucretius' libera as 'free volition'

(1) First and foremost, there is De Rerum Natura 2.251-93, where Lucretius presents what I shall call 'the libertarian argument' for the thesis that atoms swerve. Lucretius maintains that the swerve is that "whence" (unde) arises the "free volition" (libera voluntas) whereby "we likewise swerve our motions" (declinamus item motus) when and where we wish. And the natural way to read this is as claiming that swerves cause volitions from the bottom up. (I shall call this 'the argument from Lucretius.')

Purinton simply identifies swerves (one or more) with volitions

(2) Other than Lucretius, none of the authors who mention the swerve gives any account at all of the relation between swerves and volitions. That is not very surprising, if the relation between swerves and volitions is so simple that it can go without saying (as it is on my view, according to which volitions 'at bottom' just are swerves). But it would be very surprising, if Epicurus had a complicated view of the relation of swerves to volitions, such as that swerves are very rare events which are not directly linked to volitions, but function only to break the chain of causation every once in a long while (as Furley would have it) or that swerves cause us to focus on images of actions, which then cause volitions (as Fowler would have it) or that first volitions occur and then, after a short wait, swerves occur to trigger the desired bodily motion (as Englert would have it) or that swerves are caused by volitions, as emergent properties of the mind, from the top down (as Sedley would have it). For none of our sources say any such thing. (I shall call this 'the argument from silence.')

(3) Now set aside all textual evidence and simply ask what a would-be libertarian atomist is obliged to say. Since, to be a libertarian, one must say that volitions are fresh starts of motion, and since, to be an atomist, one must say that all mental events are caused from the bottom up by the motions of the mind's constituent atoms, a would-be libertarian atomist is obliged to say that volitions are caused from the bottom up by fresh starts of atomic motion. (I shall call this 'the a priori argument,' since it does not depend on any textual evidence.)

(4) At Ennead 3.1.1, Plotinus formulates the problem with Epicurus' position thus:

One must not admit the uncaused by positing vain swerves or a sudden motion of bodies which happens with no antecedent cause or a sudden volition (ὁρμή) of the soul with nothing moving it toward doing what it was not doing before. Or else, by this very thing, a greater necessity would hold the soul, that of not belonging to itself, but of being borne along with such motions as are undesired and uncaused.

Plotinus does not mention Epicurus here, but the allusions to "the uncaused" and "swerves" strongly suggest that it is Epicurus' view that Plotinus is here criticizing. And that is significant. For the objection that Plotinus makes - that we would not be in control of our own lives if we were borne along by random atomic motions - is basically Furley's objection to the view that swerves cause volitions from the bottom up. But, whereas Furley presents this as an objection to the thesis that Epicurus held such a view, Plotinus presents it as an argument against Epicurus' view. And that supports my thesis that, as a matter of historical fact, Epicurus did hold that swerves cause volitions from the bottom up. (I shall call this 'the argument from Plotinus.')

Notice, by the way, that Plotinus speaks here of "swerves" in the plural but of "volition" in the singular. This raises a question: what are we to say is Epicurus' view of volition in the singular? We can be sure that, according to Epicurus, just as a mind is at bottom a plurality of atoms, so a volition, as a motion of the mind, is at bottom the motions of a plurality of atoms. But, in a given volition, how many of these many atomic motions are swerves? All of them? Only one? Some, but neither all nor only one? My guess is that Epicurus did not believe that, in a typical volition, only one atom swerves. He rather believed that many do, and that more do the more strenuous the action; more mind-atoms swerve when one tries to turn one's body sharply, for instance, than when one tries to deviate just a little from one's path. But this is just guesswork, which I want to keep separate from my main thesis. So here is how I shall formulate in the singular my thesis that Epicurus held that volitions (in the plural) are caused by swerves from the bottom up: Epicurus held that an agent's volition (in the singular) is caused from the bottom up by that agent's mind's atoms' motions, at least one of which is a swerve.

That is my main thesis.
(Jeffrey Purinton, "Epicurus on 'Free Volition' and the Atomic Swerve,' Phronesis, 44, pp.256-59)

In Bobzien's 1998 book Determinism and Freedom in Stoic Philosophy she made a detailed analysis of arguments, especially those of Chrysippus, for the compatibilism of freedom with causal determinism.

In her book and a 1998 article in Phronesis (Vol. 43, No. 2 (May, 1998), pp. 133-175), Bobzien identified several variations on the theme of human freedom that were important in antiquity. Three of them are indeterminist freedoms, by which she means the decision is partly or wholly a matter of chance, and does not involve the character and values of the agent:

1) freedom to do otherwise: I am free to do otherwise if, being the same agent, with the same desires and beliefs, and being in the same circumstances, it is possible for me to do or not to do something in the sense that it is not fully causally determined whether or not I do it.

2) freedom of decision: a subtype of freedom to do otherwise. I am free in my decision, if being the same agent, with the same desires and beliefs, and being in the same circumstances, it is possible for me to decide between alternative courses of action in the sense that it is not fully causally determined which way I decide. 1) differs from 2) in that it leaves it undecided in which way it is possible for the agent to do or not to do something.

3) freedom of the will: a subtype of freedom of decision. I act from free will, if I am in the possession of a will, i.e. a specific part or faculty of the soul by means of which I can decide between alternative courses of actions independently of my desires and beliefs, in the sense that it is not fully causally determined in which way I decide. 2) differs from 3) in that the latter postulates a specific causally independent faculty or part of the soul which functions as a "decision making faculty."
(Phronesis, p.133)

Then in 2000 Bobzien challenged Pamela Huby's 1967 assertion that Epicurus discovered the "free will problem." She did not mention that Long and Sedley shared that view.

In 1967 Epicurus was credited with the discovery of the problem of free will and determinism. Among the contestants were Aristotle and the early Stoics.

Epicurus emerged victorious, because — so the argument went — Aristotle did not yet have the problem, and the Stoics inherited it from Epicurus. In the same year David Furley published his essay 'Aristotle and Epicurus on Voluntary Action', in which he argued that Epicurus' problem was not the free will problem. In the thirty-odd years since then, a lot has been published about Epicurus on freedom and determinism.

But it has only rarely been questioned whether Epicurus, in one way or another, found himself face to face with some version of the free will problem. In this paper I intend to take up the case for those who have questioned the point, combining a fresh perspective on the debate with a selection of new arguments and a detailed textual analysis of the relevant passages. Let me begin with a brief sketch of the problem of freedom and determinism which Epicurus is widely taken to have been concerned with.

The determinism Epicurus defends himself against is usually understood as causal determinism: every event is fully determined in all its details by preceding causes. These causes are commonly pictured as forming an uninterrupted chain or network, reaching back infinitely into the past, and as governed by an all-embracing set of laws of nature, or as manifestations of such a set of laws of nature.

Freedom to do otherwise, freedom of decision, and extreme freedom of the will Bobzien now labels "two-sided" freedom

On the side of freedom, Epicurus is generally understood to have been concerned with freedom of decision (the freedom to decide whether or not to do some action) or freedom of choice (the freedom to choose between doing and not doing some action) or freedom of the will (where the freedom to will to do something entails the freedom to will not to do it, and vice versa; I call this two-sided freedom of the will). Epicurus is taken to have introduced an indeterminist conception of free decision or free choice or two-sided free will: agents are free in this sense only if they are causally undetermined (or not fully causally determined) in their decision whether or not to act on their choice between alternative courses of action; undetermined, that is, by external and internal causal factors alike. There is assumed to be a gap in the causal chain immediately before, or simultaneously with, the decision or choice, a gap which allows the
coming into being of a spontaneous motion.

In this way every human decision or choice is directly linked with causal indeterminism. The assumption of such indeterminist free decision, free choice, or two-sided free will does not presuppose that one specifies an independent mental faculty, like e.g. a will, and indeed it is not usually assumed that Epicurus' theory involved such a faculty.

The 'free will problem' that Epicurus is assumed to have faced is then roughly as follows: If determinism is true, every decision or choice of an agent between alternative courses of actions is fully determined by preceding causes, and forms part of an uninterrupted causal chain. On the other hand, if an agent has (two-sided) freedom of the will, it seems that the agent's decision or choice must not be fully determined by preceding causes. Hence, it appears, determinism and freedom of the will (freedom of decision, freedom of choice) are incompatible.

I do not believe that Epicurus ever considered a problem along the lines of the one just described. In particular, I am sceptical about the assumption that he shared in a conception of free decision or free choice akin to the one I have sketched. (I also have my doubts that he ever conceived of a determinism characterized by a comprehensive set of laws of nature; but this is a point I only mention in passing.) To avoid misunderstandings, I should stress that I do believe that Epicurus was an indeterminist of sorts — only that he did not advocate indeterminist free decision or indeterminist free choice.

Bobzien is of course right that Epicurus did not think that our decisions were made at random with no regard for our character and values, or for our feelings and desires. This is a straw argument put up by critics of Epicurean philosophy, notably the Stoic Chryssipus and the Academic Skeptic Cicero.

But Bobzien is wrong to suggest that Epicurus did not see a problem between human freedom and the causal determinism of his fellow atomist Democritus, and that his atomic swerve was not his proposed solution to that "free will problem." She notes that

Whether Epicurus discussed free will depends on what one means by 'free will'. For example, if one intends 'free will' to render Lucretius "libera voluntas," and to mean whatever element of Epicurus' doctrine Lucretius meant to capture by this phrase, then Epicurus evidently was concerned with free will. My concern is only to show that he did not discuss a problem of free will that involves a conception of freedom of decision or choice as adumbrated in the main text. [namely, "extreme" libertarianism in which chance is the direct cause of action.]

In his 2005 study Epicurus on Freedom, O'Keefe concluded that Epicurus was mostly concerned with defending an open future against fatalism and the logical necessity of statements about future events. If it is true that there will be a sea battle on Monday, the future event is necessitated.

My own thesis is that Epicurus' main concern is not with justified praise and blame, but with preserving the rationality and efficacy of deliberating about one's future actions, although he thinks that determinism is incompatible with both. The reason for this is that a necessary condition on effective deliberation is the openness and contingency of the future, and determinism makes the future necessary. Furthermore, even though Epicurus posits the swerve in order to render causal determinism false, the sort of deterministic argument that Epicurus is concerned to rebut is the fatalist argument given in de Int. 9 and by the Megarians, which moves from considerations of future truth, to the fixity of the future, to the pointlessness of deliberation. Epicurus thinks that, if the Principle of Bivalence (the principle that every statement either is true or is false) held universally, this would make the future fixed in a way such as to render us helpless. (And so we can call my view the 'bivalence' interpretation.) Epicurus thinks that both logical and causal determinism are incompatible with the contingency of the future, and the swerve renders both false, since logical and causal determinism are mutually entailing.

The swerve plays no direct role in the production of action or the formation of character.

The main textual support for attributing this role for the swerve to Epicurus is Cicero's De fato. There is precedent for the sort of position Epicurus adopts in Aristotle's rejection of the Principle of Bivalence for similar reasons in de Int. 9. If I am right about this, to assimilate Epicurus' concerns to those of modern libertarians is highly misleading.

In order to establish the 'bivalence interpretation,' I need to go through the texts that bear on the Epicurean position regarding human freedom. Rut before doing so, let me first establish its initial plausibility by showing that none of the terminology Epicureans use when discussing human freedom preclude it, and that the sort of 'free will and determinism' problem that I take Epicurus to be concerned with is one he should be concerned with, given his ethics and psychology, whereas — even apart from considerations of how successfully the swerve addresses these problems the other sorts of free will and determinism problems should not even trouble Epicurus at all.

Epicurus is concerned to defend human freedom, but none of the terminology he uses (or that others use who report on the Epicurean position) show that he is worried about preserving the ability of an agent to do otherwise than he does, much less that he conceived of this two-way ability in libertarian terms. Libera voluntas is often translated `free will,' but depending on the context, it can mean something like 'unfettered impulse.' After all, Cicero is willing to describe even the compatibilist Chrysippus, who certainly did not have a two-sided libertarian conception of freedom of will, as wanting to free (libero) our minds from necessity of motion and to accommodate the views of those who think that the movements of our minds are voluntary (voluntarius)." (For this reason, I will usually translate voluntas as 'volition,' since it is not potentially misleading in the way 'will' is, and while I think that the Epicurean theory of libera voluntas actually ends up being something like a theory of 'unfettered impulse,' using that as a translation would be highly tendentious.)

Likewise, Epicurus says that how we act and develop "depends on us" (παρ’ ῆμᾶς) and that our actions arise through us ourselves or from us ourselves (δι’ ἡμῶν αὑτῶν or ἑξ ἡμῶν αὑτῶν). That our actions are παρ’ ῆμᾶς is compatible with them simply being caused by us (e.g., that I caused myself to walk, so that my walking "depended on me"), and need not imply that, however we act, it is "up to us" whether to act one way rather than another (e.g., that it was up to me whether or not to walk). In fact, Bobzien argues at length, and I think convincingly, that to say our actions are παρ’ ῆμᾶς is more naturally read as indicating that we are causally responsible for our actions (what she calls a 'one-sided causative' παρ’ ῆμᾶς and has no implications about free choice." To say that actions are δι’ ἡμῶν αὑτῶν or ἑξ ἡμῶν αὑτῶν also has no implications of free choice. In fact, Chrysippus defends the thesis that certain things originate "from us" (ἑξ ἡμῶν), and when the Stoics are concerned to describe precisely what type of agency we do have and are at pains to deny the thesis that freedom is a matter of having free choice between opposite actions, they say repeatedly that what is up to us is what happens through us (δι’ ἡμῶν)"

The passages which report the Epicurean views on determinism and freedom indicate that Epicurus is concerned about defending something like the view that we have moral responsibility. The much later Epicurean Diogenes of Oinoanda claims that all censure and admonition would be abolished if fate controlled what we did, and Cicero, in reporting the worry that motivates the various parties to the fate and free volition debate, says that if fate were operative, there would be no justice in either praise or blame. Epicurus, likewise, when arguing that some things 'depend on us,' says praise and blame properly attach to such things, and in his anti-fatalist argument in On Nature 25, he asserts that our practices of rebuking, opposing and reforming each other presuppose that the cause of actions is 'in ourselves.'

However, even more prominent in Epicurean thought is the theme that determinism would render us helpless. When Lucretius describes the libera voluntas that the swerve snatches from the fates, he says nothing about responsibility, praise, or blame. Instead, libera voluntas is what allows each animal to go where pleasure leads it and the mind to move itself (DRN 2 257-260). Although Lucretius' later discussions of voluntas do not mention the swerve, they do confirm that it is voluntas that allows us to act as we wish to act — to visualize what we wish to visualize, to move our limbs as we desire, etc. (DRN 4 777-780, 877-880) So, if determinism threatens this voluntas, the implication is that determinism would render us unable to act as we wish to act, to move our limbs as we will, etc.

A similar concern with fatalism lurks in Epicurus' discussion of the "fate of the natural philosophers" in Ep. Men. 133-134. Epicurus contrasts what is ἁνάγκη, which is ἁνυπεύθυνος; — 'unanswerable' or 'beyond human control' — with what is παρ’ ῆμᾶς, which is ἁδέσποτος; — 'without master' or 'autonomous.' He then goes on to say that it would better to believe in the meddling Olympian gods than to be a 'slave' to the fate of the natural philosophers, since at least one can try to placate the Olympian gods, whereas the necessity of the natural philosophers is inescapable. In On Nature 25, the target of Epicurus' argument is a fatalist: this person denies that our decisions make any difference; what we do is not a cause or explanation (aitia) of what happens.' Finally, Cicero's discussions of the Epicurean and Stoic positions in the De fato show that a major concern of theirs was whether, if what will occur in the future has always been true and always been causally determined, the future is necessary in a way that makes all deliberation and action pointless.

Now, before going through the texts, let's step back and ask: given Epicurus' ethics and his psychology, what sort of freedom should he be worried about? Epicurean ethics is egoistic and hedonistic. In every choice, one should strive to attain the 'goal of nature,' pleasure (KD 25).

The problem with most of the traditional 'libertarian' interpretations of Epicurus is that they dissociate one's actions not only from external causation but also from being caused by the psychological states of the agent present at the moment of choice: his beliefs, desires, and character, since being causally determined by these states is incompatible with a robust ability to do otherwise than one does.

Let us leave aside, for the moment, the objection that a random atomic swerving in one's mind is an unpromising basis for the production of free and responsible actions, instead of random and blameless twitches. Why should Epicureans be concerned to try to defend this sort of freedom of choice in the first place? If one has correct beliefs about the workings of the world and the limits of what is required for happiness, and one knows what one needs to do in the present situation to attain a pleasurable life, then having one's actions determined by these psychological states would not be ethically problematic — in fact, it is exactly what one would want to happen. This is the state of the Epicurean Sage. It is hard to see how having a 'two-sided' libertarian freedom of choice would help in the pursuit of ataraxia, or tranquility, which Epicurus maintains is the chief constituent of the happy life. And if this freedom would not help in the pursuit of ataraxia, it is hard to see why any good Epicurean should care about defending its possibility against the threat of determinism.

In 2005, Salles published The Stoics on Determinism and Compatibilism. In it, he makes the strongest possible case that the doctrine of Chrysippus provides enough control for agents to claim that our actions are "up to us." His evidence comes from Cicero , Alexander of Aphrodisias, and Nemesius of Emesa.

Salles discusses several aspects of Stoicism that seem to demand complete determinism.

The Principle of Bivalence: Statements about the future are already true or false. A true statement about the future necessitates future events, the causes for which must already exist.

(Tc) For any event S that occurs at some future time t, the proposition S occurs at t cannot be true now, unless there is a cause now (that is, a causal chain stretching from the present to the future time t) for S's occurring at t.

Chrysippus infers causation from prior truth through (Tc). This inference, in turn, explains why the first premiss of Chrysippus' argument: - If there were causeless events, propositions about future occurrents would lack a truth value' - holds true and, in particular, why propositions second premiss of the argument — 'propositions about future occurrents are already either true or false' — yields that no future event is causeless.

We may generalize the thesis to all times, which is Chrysippus' intended conclusion ('motus ergo sine causa nullus est'). Since in the past what is now present was in the future and what is now past was present, then, for any present event, there was in the past a true proposition asserting its future occurrence; in consequence, there was at that time a cause of its (then) future occurrence; so every event in the present has a cause; mutatis mutandis, every event in the past has a cause; thus, every event (past, present and future) has a cause. (Salles, pp.8-9)

Eternal Recurrence: After a given world-cycle, the planets are arranged as they were at the start, and everything that happened in one cycle now reoccurs. Nothing can be discernibly different (ἀπαράλλακτος).

Stoic indiscernibility is metaphysical and conveys numerical identity. It is metaphysical, as opposed to merely epistemological, because it does not mean just that no observer can register the differences — it also means that there are no differences there to be registered between them; and it conveys numerical identity because if A and B are indiscernible, A and B are not really 'two' discrete things, but rather one and the same object numerically. It is because they are indiscernible that they are in fact numerically the same. As applied to everlasting recurrence, indiscernibility implies that the world of the present cycle is the same in all respects (and hence the same even in number)" as the world of any other cycle: in the qualities of its objects, in how each of them is intrinsically disposed, and in how they are related to each other." As Nemesius indicates further down in his report: 'Everything will be just the same and indiscernible down to the smallest details.' (Salles, p.23)

Predetermination: The Stoic God foreknows everything about the world, being essentially synonymous with the laws of Nature.

Since (a) divine providence presupposes predetermination and (b) predetermination, in turn, presupposes foreknowledge. Providence implies predetermination because, to ensure that the world as a whole (in extension and duration) turns out to be as good as possible, god has to predetermine right from the start of the cycle everything that will happen and exist in it. And predetermination implies foreknowledge because god could not be said to predetermine X to happen unless he thereby acquires foreknowledge that X will happen. Divine foreknowledge is not just a sufficient condition for predetermination, but also a necessary one (god predetermines X to happen if and only if god foreknows that X will happen). (Salles, p.27)

The Future Is Already Fixed: This is a special form of Stoic fatalism.

Fatalism, or the idea that propositions about future occurrents are already true or false and that the future is already fixed, is earlier than Stoic philosophy. It is a position that was already the target of Aristotelian criticism in the difficult chapter 9 of the de interpretatione. And it is to Aristotle that we owe the objection that fatalism encourages idleness: if it is already true that I will win the elections (or already false that I will lose), why should I do a campaign? Is not a campaign superfluous? And if it is, why should I not sit back and relax until the elections? Chrysippus attempted a defence of fatalism against this objection. He provided strong reasons for thinking that fatalism does not render our actions and efforts superfluous.

Everything Has A Cause, and Causation is Necessitating: Given the same circumstances, the same effects must obtain. This idea goes back to the first Stoic, Zeno of Citium

'It is impossible that the cause be present
yet that of which it is the cause not obtain' (ἀδύνατον δ’ εἴναι τὸ μὲν αἴτιον παρεῖναι, οὖ δέ ἐστιν αἴτιον μὴ ὑπάρχειν).

Salles distinguishes three forms of determinism that can be distinguished from Stoic determinism - general determinism, crude fatalism, and external determinism.

General determinism:

General determinism holds that every counterfactual state or event is forever impossible and, correlatively, that every factual state or event is forever necessary. An example of a state that is subject to this kind of necessity — which I shall call `general' necessity — is that expressed by the factual proposition snow is cold. As a matter of fact, snow is always cold, and it cannot be hot so long as it remains snow. This proposition expresses a state that does seem to be subject to a general necessity, hut is every factual state and event subject to this kind of necessity? According to general determinism the answer should be in the affirmative. (Salles, p.xiv)

Crude fatalism:

Crude fatalism departs from general determinism in that it is compatible with the possibility of change. In particular, the crude fatalist plainly accepts that the future may differ from the present and the present from the past. However, according to crude fatalism, the future is already fixed in a way that what is due to happen, or be the case, will happen regardless of what states or events obtain in the present or the past. For example, if I am ill but am due to recover, then I will recover whether or not I call in a doctor and follow his prescriptions. More generally, the obtention of states and events at a particular time is not dependent upon the obtention of earlier states or events — a point that one may express by saying that the former would have obtained even if, per impossibile, the latter hadn't. This sheds light on an important aspect of crude fatalism: factual states and events at a particular time do not obtain because of the states or events that obtained earlier. There is no explanatory relation between past, present and future. To pursue the example, if I do call in the doctor and recover from illness, then, given that I would have recovered even if I had not called in a doctor, I did not recover because I called in the doctor. (Salles, p.xv)

External determinism

External determinism maintains that any event or state is contingent upon earlier events or states. The distinctive claim of external determinism is that the prior causes of what we do and of what we are may all be traced back to things that are external to us: our present environment, our teachers, our family and even the biological make-up of our ancestors. In consequence, everything we do and everything we are is, in fact, ultimately fully determined by external causes alone. Now, external determinism does not seem to be compatible with responsibility, either in a moral or in a legal sense of the term 'responsibility'. To take one example, I cannot be morally blamed for having missed my daughter's graduation ceremony if the reason why I missed it is that I was kidnapped by some ruffians. There is one exception to this principle: I may be responsible for something that happens to me, if it happens to me as a result of some earlier thing that I did and for which I am responsible. For example, I am morally blameworthy for being at the mercy of the ruffians who kidnapped me if the cause of my kidnap was, to some extent, my lack of care in circumstances that I knew were dangerous. However, this is precisely what external determinism denies is possible. According to external determinism, all the states or events that we supposedly bring about, or to the production of which we supposedly contribute, are ultimately fully determined by causes external to us. My lack of care, the external determinist would argue, is itself ultimately fully determined by external factors alone.

Some philosophers have argued that any form of causal determinism is, willingly or not, a form of external determinism. In fact, by the time of Aristotle, 'force', or fully external determination (βία), was already one of the connotations of the term 'necessity' (ἀνάγκη) and its cognates. (Salles, p.xvii)

Salles notes that Chrysippus deals with the threat of external determism by adding an "internality requirement," so that an event is not solely determined by factors external to us.

The philosophical question addressed is whether this `internality requirement', as I shall call it, can be met in a world governed by determinism. One major objection against compatibilism turns on this issue. The objection (henceforth the 'externalist objection') is that, if every state and event is determined by prior causes, then everything we do is in fact fully determined by external factors alone. In consequence, the internality requirement cannot be met and causal determinism would remove any possible ground for the justified ascription of responsibility. But is the externalist objection cogent? A central compatibilist argument developed by Chrysippus was designed to rebut it. On his view 'everything is determined by prior causes' does not have to imply that we are always at the mercy of purely external forces. The internality requirement, which is a necessary condition for responsibility (either legal or moral, as Aristotle claims), can in some relevant cases be perfectly met in a world governed by determinism. (Salles, p.33)

Can Salles possibly make this "perfect" case for Chrysippus' compatibilism? In fact, he says the argument contains some of the same intuitions put forward by the modern compatibilist Harry Frankfurt. The dual capacity to do something or to do otherwise is not needed, he says. But Chrysippus requires more than just automatic acceptance of an impression (φαωτασία) and assent to the impulse. What is required is critical reflection (κρίσις), similar to Frankfurt's second-order desires.

Frankfurt and Chrysippus explain moral responsibility by appealing to factors that are substantially the same. In Frankfurt's theory, the responsibility for the action derives from the agent's decision to perform it, but also from that decision's being based on a previous all-things-considered practical reflection. Similarly, the responsibility for the action in Chrysippus derives from the agent's exercise of an impulse for it (or his assenting to the impression where the action is presented as valuable), but also, and crucially, from the impulse's being fully rational, which involves a reflection concerning the all-things-considered desirability or appropriateness of the action. It is noteworthy that in some of his later works Frankfurt's account lays a certain emphasis on second-order desires: To be responsible for Φ-ing, it is sufficient to desire having the desire to Φ, provided that the former, second-order, desire is based on a previous practical reflection concerning the desirability of the latter: the agent is responsible because he came to have the desire to desire to Φ as a result of a reflection about whether the desire to Φ is worth having. Therefore, the question addressed in the reflection is mainly 'should I desire to Φ?' Its focus is a desire — whether or not one should have it. In the Chrysippean account, by contrast, the focus of the reflection is on action. As we have seen, the question it addresses is 'Is it appropriate for me to Φ (given the present circumstances)?' (Salles, p.66)

Salles discusses the difficulty that Chrysippus may have inconsistently argued, for metaphysical reasons, that alternative possibilities for action (or specifically the possibilities of assenting or not assenting) exist and that these possibilities are consistent with causal determination (p.86). Chrysippus held that though the future is causally determined and fated, it may not be logically necessitated in all senses. In spite of determinism, an individual action may be contingent. The agent may or may not perform it at a specific time. (p.69) Salles analyzes the denial of necessity as the result of two senses of necessity in Chrysippus

I Φ is capable of being true if I am fit, or strong, enough to Φ; and it is capable of being false if I have the physical strength to refrain from Φ-ing. As for the other condition — being or not being prevented by external factors (τὰ ἐκτός) from being true or false — it refers to the presence or absence of factors external to us that either prevent us from acting in a certain way or force an event or state to take place at us. In contrast with the former condition, the latter is an innovation of Chrysippus.

The non-necessity of a proposition in this modal system is compatible with there being necessitating causes for the event in question. Consider a situation where my action is to stand still. I now have the intrinsic fitness required for walking and nothing external prevents me from doing so. Therefore, the proposition I stand still now is non-necessary in the sense envisaged by this modal system. Yet, my standing still is causally necessitated, namely by the whole rational process by which I came to the conclusion that I should remain still and that caused me to act accordingly. In other words, the proposition I stand still now is non-necessary in Chrysippus' modal system, even though my action is, at the same time, necessary in a causal sense. In fact, as has been hypothesized in recent scholarship, there seems to be two kinds, or at least senses, of necessity in Chrysippean Stoicism. One sense is that required by the modal system just described, whose aim, as I shall argue in some detail later on in this section, is twofold: (i) to establish that some states and events that are counterfactual at all times are nevertheless possible; (ii) to preserve the interdefinability of the four central modal notions. It follows from (i) and (ii) that a factual action whose opposite is counterfactual at all times but possible is, thereby, non-necessary.

The other sense of necessity is that required by Stoic causation, according to which an effect is necessitated by its cause — an idea that Chrysippus never contradicted and that goes back, as we know, to Zeno: 'it is impossible that the cause be present
yet that of which it is the cause not obtain' (ἀδύνατον δ’ εἴναι τὸ μὲν αἴτιον παρεῖναι, οὖ δέ ἐστιν αἴτιον μὴ ὑπάρχειν). Thus, a factual event necessitated by its cause may nevertheless be non-necessary from the point of view of Chrysippus' modal system. There is no contradiction as long as we bear in mind that these are two different kinds or senses of necessity that were not meant by Chrysippus to be equivalent to each other. (Salles, pp.82-84)

Dorothea Frede

Frede examined the comments of Alexander of Aphrodisias in an article on the Stanford Encyclopedia of Philosophy. She says that Alexanders' treatise On Fate (which should be compared to Cicero's work On Fate) is "the most comprehensive surviving document in the centuries-long debate on fate, determinism, and free will that was carried on between the Stoics, the Epicureans and the Academic Skeptics."

It is unclear whether there had been a genuinely Peripatetic contribution to this debate before Alexander. If there was not, Alexander clearly filled a significant gap. Though Aristotle himself in a way touches on all important aspects of the problem of determinism — logical, physical, and ethical — in different works, he was not greatly concerned with this issue, nor does he entertain the notion of fate (heimarmene) as a rational cosmic ordering-force (as do the Stoics). In De interpretatione 9, he famously proposed to solve the problem of ‘future truth’ by not assigning truth-values to statements in the future tense about individual contingent events. In his ethics he deals with the question of whether individuals have free choice, once their character is settled. As Aristotle sees it, there is little or no leeway in moral decision, but he holds individuals responsible for their actions because they at least collaborated in the acquisition of their character (EN III, 1-5). In his physical works Aristotle limits strict necessity to the motions of the stars, while allowing for a wide range of events in the sublunary realm that do not happen of necessity but only for the most part or by chance (Phys. II, 4-6). Though he subscribes to the principle that the same causal constellations have the same effects, he also allows for ‘fresh starts’ in a causal series (Metaph. E 3). Given these various limitations, Aristotle had no reason to treat determinism as a central philosophical problem either in his ethics or in his physics. The situation changed, however, once the Stoics had established a rigorously physicalist system ruled by an all-pervasive divine mind. It is this radicalization of the determinist position that sharpened the general consciousness of the problematic, as witnessed by the relentless attacks of the Stoics’ opponents, most of all the Academic skeptics and the Epicureans, which lasted for centuries.

This long-standing debate prompted Alexander to develop an Aristotelian concept of fate by identifying it with the natural constitution of things, including human nature (On Fate, ch. 2-6).

Since there is always the possibility that something happens against the natural and normal order of things, there are exceptions to what is ‘fated’ and there is room for chance and the fortuitous. Most of the treatise is occupied not with the defense of this peripatetic position, but rather with attacks on the various aspects of the determinist position. Alexander claims to show why the Stoics’ attempt (though he nowhere names them) to defend a compatibilist position must fail. The determinists, he says, are neither entitled to maintain a coherent concept of luck and the fortuitous, nor of contingency and possibility, nor of deliberation and potency. The bulk of this polemical discussion concentrates on the difficulties for the Stoic position by claiming that their concept of fate makes human deliberation superfluous and therefore imports disastrous consequences for human morality and life in general (chs. 7-21). Alexander also presents, albeit in a dialectical fashion intended to lead to the defeat of the Stoic tenets, the arguments used by the Stoics in their defense of contingency, chance, and human responsibility.

As he claims time and again, the Stoics can defend the use of these terms, but only in a purely verbal sense. In addition, their notion of divine foreknowledge and prophecy turns out to be incoherent (chs. 22-35). The stringency and originality of Alexander's critique cannot be discussed here (cf. Sharples 1983; Bobzien 1998). While his presentation is not free from repetition and while the order of the arguments leaves something to be desired, it is an interesting text that displays a lively engagement with the issues and quite a bit of philosophical sophistication.

He argues that truly free action requires that at the time one acts, it is open to one both to do and not to do what one does in fact then do. Thus Alexander originates the position later known as ‘libertarianism’ in the theory of free action. Alexander's construction of an Aristotelian account of fate and divine providence that limits them to nature and its overall benign order represents quite a weak conception of fate; but it is clearly the only one that Alexander regarded as compatible with the principles of Aristotelian philosophy of nature and ethics. That the concept of fate greatly intrigued him is confirmed by the fact that he returns to the issue in his addendum (‘Mantissa’) to the treatise On the Soul and in some of his Problems (2.4.5, cf. Sharples 1983, esp. the Introduction).

John Dudley

In his definitive 2011 monograph Aristotle's Concept of Chance, Dudley makes it clear that Aristotle rejects determinism. He says that Aristotle offers three causes (ἀιτία) that are not themselves caused. These are human free choice (ἐφ' ἡμῖν), accidents (συμβεβεκός), and chance (τυχή for humans, and ταὐτόματον for animals and nature). These uncaused causes break the chain of "necessary" causes (ἀνάγκη), explain future contingency, and make the future inherently unpredictable (p.268). He says in conlusion,

It may be said, then, that Aristotle not only was not a determinist, but that he provided an epistemological and metaphysical explanation for the inadequacy of determinism. He argued profoundly not only that human free choices are not the only exception in an otherwise determined world, but that all events on earth are in the final analysis contingent, since they can all be traced back to a contingent starting-point. This contingent starting-point can be a free choice or a [sc. unusual] accident or chance, which can be based on both. Science is only possible to the extent that accidental causes can be excluded from predictions. The scope of science is, therefore, very limited. Science is dependent on the reduction of events to per se causes. However, per se causes are not sufficient to account for events. Events are, therefore, contingent.

For Aristotle it is not legitimate to view the present condition of the world as the outcome of the interaction of chains of necessary causes, as many contemporary scientists and philosophers would hold. For Aristotle the human intellect can only trace back one chain of causes at a time, and will always have to stop the process when it reaches a free choice or a [.. unusual] accidental cause, both of which introduce contingency into chains of causes, since the effect of free choices and [sc. unusual] accidents on the course of events is inherently unpredictable. While the intellect is tracing one chain of causes, the outcome or final member of any other relevant chain of causes has the status of an accident in relation to the chain of causes under construction. Thus Aristotle's rejection of determinism due to unusual causes is based on the working of the intellect in tracing individual chains of causes. If pushed to its logical conclusion, Aristotle's objection to the determinist standpoint — based on his view as set out above — would have to be of a rather Kantian nature, namely that the vision of "the world" as "the outcome of the interaction of chains of necessary causes" is an invalid mental construction, since it does not take account of [sc. unusual] accidents.
(Aristotle's Concept of Chance, p.310